identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
03B387E8FFAE320D879AFAB09D9AFC0A.text	03B387E8FFAE320D879AFAB09D9AFC0A.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Alethinophidia Nopsca 1923	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Infraorder  ALETHINOPHIDIA Nopsca, 1923</p>
            <p> Diagnosis. Vertebrae of Infraorder  Alethinophidia are variable, but can typically be identified by the presence of a neural spine, a somewhat high neural arch, and the presence of a median notch on the posterior border of the neural arch has a median notch (Rage, 1984; Holman, 2000). </p>
            <p> Remarks. While the above characters are true for most of  Alethinophidia , both Rage (1984) and Holman (2000) noted exceptions in the  Uropeltidae , which lack neural spines, and the genus  Coniophis , where the vertebrae lack both a neural spine and a median notch in the posterior neural arch. The “higher neural arch” of Rage (1984) is relative to the lower neural arch of Scolecophidia. Ikeda (2007) examined these characters in additional taxa, and stated that despite the exceptions above, the character states of Rage (1984) and Holman (2000) can be considered diagnostic. </p>
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	https://treatment.plazi.org/id/03B387E8FFAE320D879AFAB09D9AFC0A	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFAE320C84D9F8809868FC3B.text	03B387E8FFAE320C84D9F8809868FC3B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Booidea Gray 1825	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Superfamily  BOOIDEA Gray, 1825</p>
            <p>Diagnosis. There are not many vertebral characters defining the diverse group of booid snakes; the most commonly cited characters include the presence of lateral foramina and higher neural arches than those found in Anilioidea (Holman, 2000; modified from Rage, 1984; supported by Ikeda, 2007). Furthermore, in pythonids, the shape of the hemal keel is defined by grooves or depressions beginning at the cotylar rim, but projecting below the centrum only in the posterior part of each vertebra (Scanlon and Mackness, 2001; Szyndlar and Rage, 2003).</p>
            <p> Remarks. Skeletal characters used to describe  Booidea are primarily based on cranial elements (see Georgalis and Smith, 2020). In comparison to colubroids, booid vertebrae are generally less slender and elongate, and tend to have shorter and broader neural spines in at least North American species (Holman, 2000; Smith, 2013).  Booidea can often be separated from Pythonoidea based on greater intracolumnar heterogeneity in the former (Szyndlar and Rage, 2003), and thicker zygosphenes in the latter when compared to similarly sized booids, although there is some amount of variability in this character (Georgalis and Smith, 2020). </p>
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	https://treatment.plazi.org/id/03B387E8FFAE320C84D9F8809868FC3B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFAF320384B8FB499B36FE06.text	03B387E8FFAF320384B8FB499B36FE06.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Charina Gray 1849	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  CHARINA Gray, 1849</p>
            <p> Diagnosis. As diagnosed in Head (2015),  Charina possesses a lobate neural spine that is laterally expanded similar to other Charinainae, and the pterapophyses are anteriorly directed in caudal vertebrae (Kluge, 1993; Szyndlar, 1994).  Charina also exhibits a non-U-shaped zygosphene in dorsal view, a strongly concave zygosphene in anterior view, a relatively depressed neural arch, an incised posterior edge of the neural arch, and no paracotylar foramina (Holman, 2000). </p>
            <p> Remarks. The fossils described here are similar in size and morphology to known species of  Charina . The longer neural spine, the V-shaped (dorsal), strongly concave (anterior) zygosphene, and the depressed neural arch with a relatively deeply incised posterior edge suggest that these vertebrae do not belong to the genus  Lichanura ; however, it should be noted that Bell and Mead (1996) have observed some intraspecific variation in these characters. As in Parmley and Walker (2003), we instead attribute this fossil to the genus  Charina based on the relative length of the neural spine, which is greater than that of  Lichanura , and the lack of juvenile characteristics despite being relatively small in size. Parmley and Walker (2003) have observed that  Lichanura of a similar size show juvenile characteristics such as a short, high overall morphology, thin neural arch, thin and highly arched zygosphene, exceptionally short neural spine, enlarged neural canal, and a condyle that appears too large for the centrum, none of which are visible in this specimen. </p>
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	https://treatment.plazi.org/id/03B387E8FFAF320384B8FB499B36FE06	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFAF320C8651FC299DF0FB5B.text	03B387E8FFAF320C8651FC299DF0FB5B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Charinaidae Gray 1849	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Family  CHARINAIDAE Gray, 1849 (sensu Pyron et al., 2014) </p>
            <p> Diagnosis. The following vertebral osteological characters are modified from Brattstrom (1958), Kluge (1993), Bell and Mead (1996), Holman (2000), and Head (2015) to reflect the current nomenclature for Constrictores and  Booidea (Reynolds et al., 2014; Zaher et al., 2019; Burbrink et al., 2020; Georgalis and Smith, 2020). The vertebrae possess a flattened neural arch. The neural spines are low, and in the caudal vertebrae are expanded, exhibiting a somewhat distended or distally lobate appearance relative to pre-caudal neural spines (Head, 2015). Prezygapophyseal accessory processes are reduced (Holman, 2000). Paracotylar foramina are absent (Kluge, 1993). Caudal vertebrae are very short, with a variety of processes giving them a complex appearance (with the exception of the genus  Lichanura ; Holman, 2000). </p>
            <p> Remarks. Snakes of the  Charinaidae are typically small to medium in size, robust in body form, with short tails and small eyes, all of which assist them in a semifossorial lifestyle (Holman, 2000). Many North American fossil booids, including extant genera  Charina and  Lichanura , were previously assigned to the Erycinae, which are generally similar in body form, vertebral morphology, and lifestyle (Holman, 2000; see Pyron et al., 2014 and ICZN, 2020 for additional details regarding taxonomic nomenclature). Under the most recent taxonomy, North American subfamilies Charinainae Gray, 1849 (  Charina and  Lichanura ) and Ungaliophiinae McDowell, 1987 (  Exiliboa and  Ungaliophis ) are now grouped within the  Charinaidae (Pyron et al. 2014; Head, 2015; ICZN, 2020). This further complicates the fossil record of older North American snakes not found in Penny Creek, in that genera such as  Calamagras ,  Ogmophis ,  Geringophis ,  Pterygoboa , and others are left with a somewhat uncertain taxonomic status, although some research has suggested that the fossil species  Ogmophis compactus and  Calamagras weigeli may represent loxocemid and ungaliophiine snakes, respectively (Smith, 2013). An extensive apomorphy-based redescription and reorganization of the older fossil taxa may be necessary to determine if it is possible to morphologically differentiate them at the species or genus level given the newer taxonomy of extant booids (Bell et al. 2010; Pyron et al., 2014; Head, 2015). The absence of paracotylar foramina in  Charinaidae vertebrae differentiates the group from  Boidae (sensu Pyron et al., 2014). This variable character is shared with pythonids and most non-boid booids, and as such does not differentiate  Charinaidae from those groups (Kluge, 1993; Rage, 2001; Szyndlar and Rage, 2003; Georgalis, 2019; Georgalis and Smith, 2020). </p>
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	https://treatment.plazi.org/id/03B387E8FFAF320C8651FC299DF0FB5B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA032038405FDAB9C2DFA4D.text	03B387E8FFA032038405FDAB9C2DFA4D.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Caenophidia Hoffstetter 1939	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Parvorder  CAENOPHIDIA Hoffstetter, 1939</p>
            <p> Diagnosis. The vertebral synapomorphies of crown  Caenophidia include well-developed prezygapophyseal accessory processes, synapophyses that are well-differentiated into para- and diapophyseal articular facets, the presence of pleurocentral hypapophyses throughout the precloacal vertebral column, the presence of one or more paracotylar foramina, a condyle and cotyle that are relatively small (compared to Constrictores) and circular to ovoid and elongate in cross section, and well-developed paralymphatic channels that define the lateral margins of a distinct hemel keel (Holman, 2000; Head et al., 2016). </p>
            <p> Remarks. The vertebral morphologies of Caenophidians is markedly different from that of  Booidea , including many of the most notable components of a snake vertebrae (e.g., neural spine, centrum, synapophyses, etc.). The works of Head (2015) and Head et al., (2016) to provide fossil calibration dates for snakes also summarize the morphological synapomorphies that differentiate these groups after the taxonomic restructuring of  Caenophidia by Zaher et al. (2009), and Constrictores by Pyron et al. (2014), and Georgalis and Smith (2020). </p>
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	https://treatment.plazi.org/id/03B387E8FFA032038405FDAB9C2DFA4D	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA0320387A1FE299C03FD86.text	03B387E8FFA0320387A1FE299C03FD86.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Charina prebottae Brattstrom 1958	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Charina cf. Charina prebottae Brattstrom, 1958 † </p>
            <p>Figure 5</p>
            <p>Material. UNSM 139981 (posterior middle trunk vertebra).</p>
            <p>Description. The vertebra appears near square in shape from dorsal view, but is slightly wider at the prezygapophyses than the postzygapophyses. The postzygapophyses are rounded, while the prezygapophyses are moderately pointed with reduced accessory processes, and are raised antero-laterally. The neural spine is low, broad, and is longer than it is tall or wide. The top of the neural spine is weathered, but this does not appear to affect the overall shape of the neural spine in dorsal view. The neural spine tapers in width anteriorly and is incised posteriorly. The zygosphene is dorsally flat and v-shaped overall, with somewhat rounded lateral edges that extend slightly forward on the anterior face. In anterior view, the zygosphene is concave. The neural arch is somewhat flattened and deeply incised posteriorly. The cotyle is round and mildly angled ventrally, with the dorsal edge extending more anteriorly and the ventral edge extending more posteriorly. Paracotylar foramina are absent. The hemal keel is wide, flat, and smooth ending just before reaching the condylar head. It is bordered laterally by a flat indentation, primarily on the anterior end.</p>
            <p> Remarks. The fossil described here is similar in size and morphology to known species of  Charina (see above for description and comparisons with  Lichanura ). It is most similar to  Charina prebottae specimens from other Nebraska localities, as it possesses a more strongly developed hemal keel when compared to the same vertebral region in extant species of  Charina (Holman, 1987) and no break in the slope of the anterior neural spine in lateral view as it descends to the zygosphene (Bell and Mead, 1996). Other characters described by Brattstrom (1958) for  C. prebottae may represent individual and intracolumnar variation as well as differences between his fossils from California and the fossils from Nebraska. Holman (2000) noted that  Charina prebottae also exhibits notable variation across a wide geographic area throughout the Miocene. Previous literature suggests that  C. prebottae may be a catch-all taxon for multiple species, as Brattstrom’s (1958) un-illustrated account and subsequent illustrated accounts do not completely match, warranting further in-depth study (Bell and Mead, 1996; Holman, 2000). Although this vertebra is weathered and missing the extreme parts of several of its structures, it exhibits features of the neural spine (Brattstrom, 1958; Bell and Mead, 1996) and hemal keel (Holman, 2000) matching those of  C. prebottae . As such, we confer this vertebra to  C. prebottae until the taxon is more comprehensively assessed and re-diagnosed. </p>
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	https://treatment.plazi.org/id/03B387E8FFA0320387A1FE299C03FD86	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA232018786F9FC9DB1FB06.text	03B387E8FFA232018786F9FC9DB1FB06.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Colubroidea Oppel 1811	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Superfamily  COLUBROIDEA Oppel, 1811</p>
            <p> Diagnosis. Vertebral characters used to identify to  Colubroidea include: vertebrae longer than wide (length at least 1.2-1.3 times as wide at the neural arch) and relatively lightly built (Holman, 2000; Smith, 2013); neural spines thin and long when compared to other groups (Holman, 2000); zygosphenal and zygantral areas less massive than in booids (Holman, 2000); synapophyses distinctly divided into parapophyseal and diapophyseal processes (Holman, 2000); mid- and posterior trunk vertebrae with sharp, relatively thin hemal keels, with hypapophyses often absent in these regions (Rage, 1984; Holman, 2000; Ikeda, 2007; Smith, 2013; Head et al., 2016). When present, trunk vertebral hypapophyses are relatively long and often pointed (Holman, 2000; Ikeda, 2007); both paracotylar and lateral foramina present (Rage, 1984; Ikeda, 2007). </p>
            <p> Remarks. There is some disparity in what constitutes the defining characters of colubroid vertebrae because of the vast diversity of the group. As such, we saw it fitting to summarize known characters in this study. Zaher et al. (2009, 2019) point out that no known vertebral synapomorphies currently define  Colubroidea , and vertebrae are typically assigned through the combination of the characters listed above. However, Rage (1984) and Ikeda (2007) identified the presence of both paracotylar and lateral foramina together on the vertebrae as consistent throughout the group. Holman (2000) provided a number of additional characters, but some of the proposed characters describe only some groups of colubroids, and as such, are not included in the diagnosis of the group at this time. These disputed characters include the lack of hypapophyses beyond the cervical region in several groups, and possibly the presence of well-developed prezygapophyseal accessory processes, which Ikeda (2007) was unable to find in several Asian viperids. It should be noted that Holman (2000) focused only on North America colubroids, and therefore may have defined the group primarily for North American taxa. </p>
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	https://treatment.plazi.org/id/03B387E8FFA232018786F9FC9DB1FB06	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA2320084D7FB2B9B34FC9B.text	03B387E8FFA2320084D7FB2B9B34FC9B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Colubridae Oppel 1811	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Family  COLUBRIDAE Oppel, 1811</p>
            <p> Diagnosis. Vertebral characters of  Colubridae include: trunk vertebrae lightly built and longer than wide (Holman, 2000); neural spines long, thin, uniformly wide, and as high as or higher than they are long (Holman, 2000; Head et al., 2016); subcentral ridges of the centrum are deep (Holman, 2000; Jurestovsky, 2021); prezygapophyseal accessory processes are prominent (Holman, 2000); epizygophyseal spines extending posteriorly from the postzygapophyses present in some species (Holman, 2000); synapophyses distinctly divided into diapophyses and parapophyses (Holman, 2000); cotyle circular-to-oval in shape (Jurestovsky, 2021). The hemal keel is typically thin and may appear similar to one of three types: hemal keels present without parapophyseal process development, both hypapophysis and parapophyseal processes present, and hemal keel thin with somewhat round prezygpophyseal articular processes (Rage, 1984; Holman, 2000; Ikeda, 2007). </p>
            <p> Remarks. The defining characters for colubrids are complicated by the diversity and degree of variation within the group, and are partially dependent on whether groups such as the natricids and dipsadids are included within the group. Post-cervical hypapophyseal characters would seem to be inappropriate for defining colubrids as a whole if natricids are included because, as noted in Ikeda (2007), several studies have pointed out that some natricids lack hypapophyses on their trunk vertebrae (McDowell, 1961; Malnate, 1972), while a small number of homalopsine snakes exhibit prominent hypapophyses on their trunk vertebrae (Gyi, 1970; McDowell, 1987). Furthermore, Ikeda (2007) noted the highly variable shape of the prezygapophyseal facets and hemal keel within  Colubridae , and pointed out that the neural spine is often more long than high in small-bodied species, but more high than long in large-bodied species. </p>
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	https://treatment.plazi.org/id/03B387E8FFA2320084D7FB2B9B34FC9B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA33200867CFC899C21FEBB.text	03B387E8FFA33200867CFC899C21FEBB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Colubrinae Oppel 1811	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Subfamily  COLUBRINAE Oppel, 1811</p>
            <p>Diagnosis. Holman (2000) outlined some general osteological characters for colubrine snakes, which were later examined and modified by Ikeda (2007). The trunk vertebrae are typically longer than wide, are often lightly built, and lack hypapophyses (Holman, 2000; Ikeda, 2007; Ikeda et al., 2016). The neural spines are somewhat thin, tall, mostly uniform in width, and often project posteriorly over adjacent vertebrae (Holman, 2000). The prezygapophyseal accessory processes are well-projected and prominent (Holman, 2000; Ikeda, 2007; Ikeda et al., 2016). The hemal keels are well-projected from the centrum and may or may not be relatively thin (Holman, 2000; Ikeda, 2007; Ikeda et al., 2016), and the subcentral ridges and grooves are distinct (Holman, 2000, Ikeda, 2007; Ikeda et al., 2016). Epizygapophyseal spines may or may not be present (Holman, 2000).</p>
            <p> Remarks. While Holman’s (2000) diagnosis of colubrines appears to fit North American taxa, Ikeda (2007) noted that the lightly build vertebrae and relatively thin hemal keels are not features consistent with some non-North American taxa, as these features show various states amongst extant species. These characters may only be consistently useful for North American taxa, and should not preclude taxa from being assigned to the subfamily  Colubrinae if those characters are not present as described in Holman (2000). Furthermore, Head et al. (2016) point out that while a precloacal vertebral column without hypapophyses have been traditionally used to differentiate colubrines from natricids and elapids (Bell et al., 2004; Szyndlar, 2012), this absence also occurs in a number of dipsadid and elapid taxa as well (Dowling and Duellman, 1978 after Pyron et al., 2013). This character therefore cannot fully diagnose colubrines to the exclusion of other clades on its own (Head et al., 2016). </p>
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	https://treatment.plazi.org/id/03B387E8FFA33200867CFC899C21FEBB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA3320784F9FEA998E2FDA6.text	03B387E8FFA3320784F9FEA998E2FDA6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Lampropeltis Fitzinger 1843	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  LAMPROPELTIS Fitzinger, 1843</p>
            <p> Diagnosis.  Lampropeltis vertebrae are somewhat robust, relatively short, and wide for a colubrine (centrum about as wide as long; Parmley, 1987), with long neural spines that are moderate to low in height, overhang posteriorly, and are either straight or overhanging anteriorly (Auffenberg, 1963; Meylan, 1982; Parmley, 1988; Parmley, 1990). The neural spines may also be thickened dorsally (LaDuke, 1991). The neural arches are depressed and wide (Auffenberg, 1963; Meylan, 1982; LaDuke, 1991; Holman, 2000). The hemal keel is well-developed and usually widened posteriorly, with well-developed subcentral ridges that curve inward near the cotyle (Auffenberg, 1963; Meylan, 1982; Parmley, 1988), and may be bordered laterally by fossae (LaDuke, 1991). The cotyle is round (Auffenberg, 1963), the condyle is round and sometimes obliquely tilted upwards (Parmley, 1990), the zygosphenes are flat anteriorly (LaDuke, 1991) and epizygapophyseal spines are absent (Auffenberg, 1963; Holman, 2000). </p>
            <p> Remarks.  Lampropeltis vertebrae differ from those of  Pantherophis and  Pituophis in exhibiting more pronounced subcentral ridges, less vaulted neural arches, and relatively lower neural spines (Parmley, 1990). They may additionally differ from  Pantherophis and  Arizona in being relatively longer and more robust (LaDuke, 1991).  Lampropeltis vertebrae differ from those of  Rhinocheilus in being relatively longer, with relatively thinner and taller neural spines that do not project anteriorly beyond the zygosphene, narrower hemal keels, relatively wider cotyles, larger zygapophyses, and more developed subcentral ridges (Van Devender and Mead, 1978; LaDuke, 1991). </p>
            <p> Holman (2000) suggested that  Lampropeltis vertebrae are more easily diagnosed on a speciesby-species basis, as there are greater differences among some species of  Lampropeltis than there are among some other colubrine genera (such as  Coluber and  Masticophis ). This idea was reexamined and discussed in Parmley and Hunter (2010), who found that  Lampropeltis alterna and the  Lampropeltis pyromelana-zonata grouping have diagnostic vertebral characters distinct from each other and from the rest of the genus, while  Lampropeltis getula ,  Lampropeltis calligaster , and  Lampropeltis triangulum form a discernable  L. getula complex. Furthermore, Auffenberg (1963) noted that smaller species appeared to have neural spines that are relatively shorter in height compared to larger species and that the hemal keel showed variation in development between species and age groups. Where exactly the known fossil species of  Lampropeltis fall within the genus could therefore be dependent on the ability to discern between these three main morphospaces on a case-by-case basis. A better understanding of these morphospaces and the morphology of fossil species could also help determine when the genus started exploring the various morphologies associated with these groupings. </p>
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	https://treatment.plazi.org/id/03B387E8FFA3320784F9FEA998E2FDA6	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA43207866BFD4E9A91FCA6.text	03B387E8FFA43207866BFD4E9A91FCA6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Lampropeltis similis Holman 1964	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Lampropeltis similis Holman, 1964 † </p>
            <p>Figure 6</p>
            <p>Material. UNSM 139982 (14 pre-cloacal trunk vertebrae).</p>
            <p>Description. In anterior view, the neural arch is moderately vaulted. The cotyle is a depressed oval bordered by deeply excavated pits, and is slightly larger than the ventrally restricted, inverted Ushaped neural canal. The zygosphene curves dorsally, and the prezygapophyseal articular facets tilt slightly upward. The diapophyses and parapophyses are distinct elements of the parapophyses, with the latter portion more distally pointed than the former; however, they are not as clearly separated as in most other colubrids.</p>
            <p>In dorsal view, the vertebrae are approximately as long as they are wide at the prezygapophyses, and the width at the well-developed, rounded prezygapophyseal accessory processes is greater than it is long through the zygapophyses. The neural spine tilts slightly ventrally in its anterior portion. The prezygapophyseal articular facets are oval to ovoid and slightly tilted upward. The epizygapophyseal spines are absent. The anterior edge of the zygosphene is slightly convex to slightly sinuate; the posterior notch of the zygosphene is Vshaped.</p>
            <p>In lateral view, the neural spine is significantly longer than it is tall, and dips slightly downward cranially. The hemal keel is visible and quite strong.</p>
            <p>In posterior view, the neural arch is moderately vaulted, and the condyle is a dorso-ventrally depressed oval.</p>
            <p>In ventral view, the strong hemal keel is spatulate or oblong in shape, but not wide throughout most of its length. Subcentral ridges are present and concave from below, but not exceptionally developed. The postzygapophyseal articular facets are ovoid.</p>
            <p> Remarks. These vertebrae in particular appear to be more similar to the general morphology of the milksnakes of the  Lampropeltis triangulum complex or the kingsnake  Lampropeltis calligaster as opposed to the  L. alterna or  L. pyromelana-zonata groupings. They possess long neural spines, moderately depressed neural arches, distinct hemal keels with deep subcentral grooves, and robust, distinct subcentral ridges (Parmley, 1990; Parmley and Hunter, 2010). More specifically,  L. similis has previously been described as similar in appearance to  L. triangulum ; however,  L. similis possesses a less depressed neural arch in the trunk region (more similar to that of  L. calligaster ) with an inverse U-shaped rather than depressed ovoidshaped neural canal, a thinner hemal keel. Holman (2000) also stated a centrum that “is not as triangular from below” as an additional apomorphy for  L. similis , but we are unable to confirm this as a consistent character throughout the vertebral column of the species. </p>
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	https://treatment.plazi.org/id/03B387E8FFA43207866BFD4E9A91FCA6	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA4320684F6FC4A9C6CF8D4.text	03B387E8FFA4320684F6FC4A9C6CF8D4.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Pantherophis Fitzinger 1843	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  PANTHEROPHIS Fitzinger, 1843</p>
            <p> Diagnosis. The vertebrae of North American  Pantherophis are relatively short, but robustly built compared to most of their contemporary colubrids. The vertebrae have wide, high neural spines and broad hemal keels, but lack epizygapophyseal spines (Holman, 2000; Parmley and Hunter, 2010). The parapophyseal process is poorly developed on either side, and the interzygapophyseal ridge is straight in lateral view (Ikeda, 2007). </p>
            <p> Remarks. The vertebrae of North American  Pantherophis are similar to some species of other large-bodied colubrine genera. In North America, the vertebrae of  Pantherophis differ from those of New World  Masticophis and  Coluber in that they are relatively shorter and more robustly built, have higher and wider neural spines, have wider hemal keels, and lack epizygapophyseal spines (Holman, 2000).  Pantherophis generally differs from  Lampropeltis in possessing a higher, more vaulted neural arch, a higher neural spine (compared to at least some species of  Lampropeltis ), straight and less defined subcentral ridges, and less robust vertebrae (Holman, 2000; Parmley and Hunter, 2010).  Pantherophis differs from  Pituophis in having a lower neural spine and a zygosphene that is rarely or never concave (Auffenberg, 1963).  Pantherophis differs from  Drymarchon in possessing a zygosphene that is rarely or never concave, greater posterolateral curvature of the neural arch, less posterior curvature of the neural spine, and a deeper concavity on the posteromedial portion of the neural arch (Jasinski and Moscato, 2017). There has been no work to definitively separate the vertebral morphology of  Pantherophis and Elaphe, in part because their reclassification as separate genera has not been morphologically defined since their separation in Utiger et al. (2002). </p>
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	https://treatment.plazi.org/id/03B387E8FFA4320684F6FC4A9C6CF8D4	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA5320484F9F8F89B54FA5B.text	03B387E8FFA5320484F9F8F89B54FA5B.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Pantherophis kansensis Gilmore 1938	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Pantherophis kansensis Gilmore, 1938 † </p>
            <p>Figure 7</p>
            <p>Material. UNSM 139983 (21 pre-cloacal trunk vertebrae).</p>
            <p>Description. In anterior view, the neural spine is relatively low for a colubrid, the neural arch is moderately vaulted, and the zygosphene is convex dorsally. The zygosphenal articular facets are strongly tilted dorso-ventrally. The neural canal is rounded and slightly smaller than the cotyle, which is also round. The prezygapophyseal articular facets tilt slightly upward, and the diapophyses and parapophyses are rounded, distinct sections of the synapophyses.</p>
            <p>In dorsal view, the neural spine is long and located in the middle of the vertebra. The anterior edge of the zygosphene is concave. The prezygapophyseal accessory processes are moderately pointed, the prezygapophyseal articular facets are rounded to oval and tilted slightly upward, and the epizygapophyseal spines are absent. The posterior edge of the neural arch in dorsal view is slightly rounded.</p>
            <p>In lateral view, the neural spine is approximately twice as long as it is high. The condyle is tilted slightly forward. The hemal keel is distinct from the centrum, and the synapophyses can clearly be divided into diapophyseal and parapophyseal sections. The interzygapophyseal ridge is bowed downward, and the subcentral ridge is bowed upward.</p>
            <p>In posterior view, the neural arch is somewhat vaulted. The condyle is round and approximately the same size as the neural canal, which is an inverted U-shape. The zygosphenal articular facets and the postzygapophyseal articular facets are all tilted sharply upward. The diapophyses and parapophyses are distinct parts of the synapophyses.</p>
            <p>In ventral view, the centrum is triangular and bordered by visible subcentral ridges. The hemal keel is well-developed, moderately wide, and constricted in the middle relative to the ends. The prezygapophyseal accessory processes are distinct, oblique, and directed anterolaterally. As in other views, the synapophyses are distinctly divided into the diapophyses and parapophyses.</p>
            <p> Remarks.  Pantherophis kansensis has vertebrae with a lower neural spine and more anterolaterally directed prezygapophyseal accessory processes than any other known species of  Pantherophis or  Bogertophis . This neural spine is relatively taller in some specimens, and is more proportionally more similar to  Pantherophis obsoletus in that regard; these vertebrae appear to be from a more anterior portion of the vertebral column. </p>
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	https://treatment.plazi.org/id/03B387E8FFA5320484F9F8F89B54FA5B	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA732048797FA499D52FCFB.text	03B387E8FFA732048797FA499D52FCFB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salvadora Baird and Girard 1853	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  SALVADORA Baird and Girard, 1853</p>
            <p> Diagnosis. Generally,  Salvadora can be identified by the combination of the following characters: (1) a thin, relatively low neural spine that gets shorter posteriorly through the trunk region; (2) obsolete to absent epizygapophyseal spines; (3) vertebrae that are approximately as wide as they are long; and (4) dorsally convex subcentral ridge in lateral view (Holman, 1973). </p>
            <p> Remarks. The delicate neural spine and invariably thin hemal keel is similar to that found in other North American colubrids such as  Coluber or  Masticophis . However,  Salvadora can be identified separately from those taxa on the basis of a proportionally shorter vertebra that appears to be nearly as wide as it is long, whereas the other two taxa appear elongate, more dorsally convex subcentral ridges, and obsolete to absent epizygapophyseal spines.  Pantherophis ,  Pituophis , and  Lampropeltis possess more robust and relatively wider vertebrae with less delicate neural spines and broader hemal keels than those of  Salvadora . Jurestovsky (2021) also noted that extant  Salvadora differ from  Carphophis ,  Diadophis , and  Gyalopion in possessing longer, more pointed accessory processes and a uniformly thinner hemal keel.  Carphophis also possesses a narrower zygosphene, more elongate centrum, a shorter neural spine, less laterally directed postzygapophyses, and a less dorsoventrally tall cotyle (Jurestovsky, 2021).  Salvadora has less robust postzygapophyses than  Diadophis and possesses a more elongate centra, a taller neural spine, and a dorsoventrally taller cotyle than in  Gyalopion (Jurestovsky, 2021) . </p>
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	https://treatment.plazi.org/id/03B387E8FFA732048797FA499D52FCFB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFA7321A84E0FCEC9B9CFBBB.text	03B387E8FFA7321A84E0FCEC9B9CFBBB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Salvadora paleolineata Holman 1973	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Salvadora paleolineata Holman, 1973 † </p>
            <p>Figure 8</p>
            <p>Material. UNSM 139984 (8 pre-cloacal trunk vertebrae).</p>
            <p>Description. The description is similar to Holman (2000) unless otherwise noted. In anterior view, the cotyle is a slightly depressed oval bookmarked by relatively large paracotylar foramen to each side. The neural canal is similar in size to the cotyle and is an inverted U-shape with medially convex sides to the neural arch. The zygosphene is dorsally convex in this view. The prezygapophyses are tilted slightly upward, and the prezygapophyseal accessory processes are well developed.</p>
            <p>In dorsal view, the vertebra is approximately as wide as it is long. The neural spine is thin and slightly overhangs the neural arch posteriorly. The zygosphene is slightly convex anteriorly. The prezygapophyseal articular facets are subrounded, and the prezygapophyseal accessory processes are approximately two-thirds as long as the width of the prezygapophyseal articular facets and are well-developed and moderately pointed. The diapophyses are only somewhat directed laterally and are barely visible from this orientation.</p>
            <p>In lateral view, the neural spine is delicate and is low, over three times as long as it is tall, with a slight anterior and posterior overhang. The subcentral groove is relatively deep, with dorsally convex subcentral ridges and a clear, uniform hemal keel. The condyle is tilted somewhat postero-dorsally, while the cotyle is oriented slightly antero-ventrally. The lateral foramen is positioned near the center of the vertebrae in this orientation, just below the interzygapophyseal ridge. Epizygapophyseal spines are absent.</p>
            <p>In posterior view, the subcentral ridges are well-developed and narrow, and the hemal keel is strongly developed and uniformly thin. The postzygapophyseal articular facets are subrounded. The condyle is a slightly depressed oval. Epizygapophyseal spines are absent, as also seen in the lateral orientation.</p>
            <p>In ventral view, the zygosphene is slightly convex anteriorly. The prezygapophyseal accessory processes are well developed. The hemal keel is uniformly thin. Both the cotyle and the condyle are oval in shape and the condyle extends to be approximately even with the postzygapophyseal articular facets.</p>
            <p> Remarks. According to Holman (2000) and our own comparisons, the vertebrae from Penny Creek assigned to  S. paleolineata are primarily from the middle trunk region, as noted by neural spines somewhat taller than in the type specimen and the larger condylar-cotylar articulation. As in Holman’s description, none of the specimens appear to have epizygapophyseal spines; as such, taxonomic assignment to  S. paleolineata is possible.  S. paleolineata is suggested as an ancestral species to modern  Salvadora species, which differ only in possessing obsolete epizygapophyseal spines (see description of genus above; Holman, 1973).  S. paleolineata also differs from  Coluber and  Masticophis in vertebral proportions, where the former has proportionally shorter, wider vertebrae and less dorsally convex subcentral ridges, as well as in the complete absence of epizygapophyseal spines (Holman, 2000).  Dakotaophis greeni possesses smaller zygapophyseal articular facets than  S. paleolineata , and the articular facets are more elongate or oval in shape and oriented less laterally (Holman, 2000). It is possible that, as in  Heterodon /Paleoheterodon, there may be greater morphological differences in the elements of the skull, should they ever be found for this species. </p>
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	https://treatment.plazi.org/id/03B387E8FFA7321A84E0FCEC9B9CFBBB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFB9321A867AFBA99A94FCBB.text	03B387E8FFB9321A867AFBA99A94FCBB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Dipsadidae Bonaparte 1838	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Family  DIPSADIDAE Bonaparte, 1838</p>
            <p> Diagnosis. Vertebrae can be assigned to  Dipsadidae through a combination of characters that individually are not necessarily exclusive to the group. Dipsadid snakes generally have vertebrae that are square to slightly longer than wide in dorsal view, an elongated centrum, and long, low, and narrow neural spines that overhang posteriorly (some taxa also overhang anteriorly) (Holman, 2000; Parmley and Hunter, 2010; Holman et al., 2011; Mead and Steadman, 2017; Jurestovsky, 2021; Syromyatnikova et al., 2021). The neural arch is depressed to moderately vaulted in different species, and the zygosphene is usually crenate, but can be concave in some species when viewed dorsally (Holman, 2000; Mead and Steadman, 2017). The prezygapophyses generally protrude only slightly beyond the ovoid prezygapophyseal facets to form small points (Mead and Steadman, 2017). The cotyle and condyle are round to slightly dorsoventrally compressed, where the cotyle is flattened on the ventral portion in anterior view (Mead and Steadman, 2017; Jurestovsky, 2021) Epizygapophyseal spines are absent (Holman, 2000; Mead and Steadman, 2017; Jurestovsky, 2021). The synapophyses are divided into distinct diapophyses and parapophyses (Holman, 2000; Syromyatnikova et al., 2021). Distinct hemal keels with adjacent subcentral ridges are present, and hypapophyses are absent from trunk vertebrae except potentially in a few species (Holman, 2000; Ikeda, 2007; Head et al., 2016; Mead and Steadman, 2017; Syromyatnikova et al., 2021) </p>
            <p>Remarks. The vertebrae of many extant dipsadid snakes have not yet been described and is outside the scope of this study, making it difficult to confirm the above characters across the entire group. We have, however, assembled the common characters expressed across several publications (Holman, 2000; Parmley and Hunter, 2010; Holman et al., 2011; Mead and Steadman, 2017; Jurestovsky, 2021; Syromyatnikova et al., 2021) – and our personal observations of some North American and West Indian taxa – as a way to delimit dipsadids from colubrids and natricids through a combination of characters.</p>
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	https://treatment.plazi.org/id/03B387E8FFB9321A867AFBA99A94FCBB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFB9321984ECFCA99868FC86.text	03B387E8FFB9321984ECFCA99868FC86.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Heterodon Latreille 1801	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  HETERODON Latreille, 1801 (in Sonnini and Latreille, 1801) or PALEOHETERODON Holman, 1964 † </p>
            <p> Diagnosis. The trunk vertebrae of  Heterodon and Paleoheterodon can exhibit a very depressed to slightly more vaulted neural arch (though relatively depressed overall compared to other dipsadids), a narrow neural spine that is longer than it is high, and a wide but flattened hemal keel (Holman, 2000). The vertebrae are slightly more long than wide, including the centrum, but still somewhat squarish appearance (Holman, 2000). The zygpophyseal articular facets are ovoid, and the prezygapophyseal accessory processes are moderately well-developed, end in somewhat obtuse points, and extend just beyond the prezygapophyseal articular facets (Holman, 2000; Mead and Steadman, 2017; Jurestovsky, 2021). The condyle and cotyle are mostly round but may be slightly dorso-ventrally compressed and flattened on the ventral side; both are similar in size to the neural canal (Holman, 2000). The synapophyses are divided into distinct diapophyses and parapophyses. Subcentral ridges are present adjacent to the hemal keel but are not prominent, the epizygapophyseal spines are absent, and hypapophyses are absent from post-cervical vertebrae (Holman, 2000). The zygosphene is variably crenate/convex or concave (Holman, 2000). </p>
            <p> Remarks. Though it is possible to identify trunk vertebrae to genus for  Heterodon or possibly Paleoheterodon, individual vertebrae of this group are difficult to distinguish at the species level. They share most diagnostic features with the genus  Farancia , but the vertebrae of  Farancia generally exhibit greater anteroposterior compression (leading to a laterally wider appearance overall; Jurestovsky, 2021) a more vaulted neural arch, and a neural spine that is more deeply undercut both anteriorly and posteriorly than in  Heterodon (Holman, 2000) . Vertebrae associated with specimens previously assigned to Paleoheterodon may show the same differences from  Farancia as  Heterodon , except in the neural arch, which overlaps with both  Farancia and  Heterodon in how depressed/vaulted the shape of that region is (Holman, 2000; Parmley and Hunter, 2010; Head et al., 2016).  Farancia and the  Heterodon /Paleoheterodon group are both identifiable within  Dipsadidae in possessing comparatively flattened and depressed neural arches (Head et al., 2016), longer than high neural spines (Jurestovsky, 2021) and wide, relatively flat hemal keels (Holman, 2000, Jurestovsky, 2021). </p>
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	https://treatment.plazi.org/id/03B387E8FFB9321984ECFCA99868FC86	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBA321987BCFCAB9D0FF9C6.text	03B387E8FFBA321987BCFCAB9D0FF9C6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Heterodon Latreille 1801	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Heterodon Latreille in Sonnini and Latreille, 1801 or Paleoheterodon Holman, 1964 † sp. indet. </p>
            <p>Figure 9</p>
            <p>Material. UNSM 139985 (12 pre-cloacal trunk vertebrae).</p>
            <p>Description. In dorsal view, the vertebrae are nearly square to slightly longer than wide. The anterior edge of zygosphene is convex, and the prezygapophyseal facets, when preserved, are ovoid in shape. The prezygapophyseal accessory processes are well-developed and the tips are moderately pointed to obtuse. Epizygapophyseal spines are absent. The postzygapophyseal accessory processes are ovoid in shape.</p>
            <p>In anterior view, both articular facets are visible on the synapophyses. The cotyle is mostly round, but sometimes slightly taller than wide. The neural arch is depressed. The neural canal is similar in shape to a ventrally restricted semi-cylinder, even somewhat squarish, and similar in size to the cotyle. The cotyle is somewhat dorso-ventrally compressed, with well-excavated pits on either side.</p>
            <p>In lateral view, the neural spine is longer than it is tall, somewhat depressed, and is typically more undercut posteriorly than anteriorly. In posterior view, the shape of the condyle is a dorso-ventrally compressed oval, and similar overall to the cotyle.</p>
            <p>In ventral view, the hemal keel generally is weak, wide, and oblong, and very depressed to flat. In some specimens, the hemal keel is slightly more distinct, and is slightly constricted between the synapophyses, indicating a more anterior trunk position for these vertebrae. The subcentral ridges are indistinct. The centrum itself is longer than it is wide.</p>
            <p> Remarks. The somewhat more vaulted nature of the neural arch in the specimens from Wt 13B when compared to extant  Heterodon vertebrae (a morphological difference also shared with  Farancia , as stated by Head et al., 2016) would previously have suggested that these fossils belong to or are comparable to  Heterodon (or Paleoheterodon)  tiheni , a species that is more easily determined based on skull morphology, rather than vertebral morphology (Holman, 1964; Holman, 2000; Parmley and Hunter, 2010). However, Parmley and Hunter (2010) determined that this neural arch character showed considerable and overlapping variation in specimens assigned to Paleoheterodon and  Heterodon , and that vertebral characters are not sufficient to differentiate between the two taxa. Unfortunately, we lack reproducible or statistical data on both the variation and the degree of overlap between these taxa, as both Holman (1977; 2000) and Parmley and Hunter (2010) included only personal observations on the topic. Furthermore, these vertebrae lack the apomorphies of the fossil species  Heterodon meadi , which exhibits a zygosphenal groove and anteroposteriorly directed sculpturing on the neural arch, but lacks skull elements to clarify its association with  Heterodon /Paleoheterodon (Jurestovsky, 2021). Similarly, the unnamed but potentially different taxon from the Sappa Creek Fauna in Kansas also lacks cranial elements (Holman et al., 2011). Because we presently do not have enough information regarding both vertebral and skull characters to confidently differentiate these taxa, and because these taxa overlap temporally (albeit in younger deposits; Parmley and Hunter, 2010), we describe it here as  Heterodon or Paleoheterodon of an indeterminate species. Future work using quantitative and morphometric methods with isolated skeletal elements may potentially help untangle this taxonomic issue. </p>
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	https://treatment.plazi.org/id/03B387E8FFBA321987BCFCAB9D0FF9C6	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBA321884E3F9EB9C63F9BE.text	03B387E8FFBA321884E3F9EB9C63F9BE.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Natricidae Bonaparte 1840	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Family  NATRICIDAE Bonaparte, 1840</p>
            <p>Diagnosis. North American natricid vertebrae have well-developed, pointed hypapophyses directed posteriorly on the trunk vertebrae (Holman, 2000). These hypapophyses are usually sigmoid in shape (Szyndlar, 1991). The vertebrae overall are lightly built and elongate, with long centra, strong subcentral ridges, posteriorly vaulted neural arches, and somewhat short parapophyseal processes (Szyndlar, 1991).</p>
            <p>Remarks. Szyndlar (1991) differentiated natricid snakes from other snake groups known to possess hypapophyses on their trunk vertebrae. Natricids differ from viperids in exhibiting hypapophyses that are somewhat sigmoidal in shape, and in possessing a relatively longer centra, posteriorly vaulted neural arches, and shorter parapophyseal processes. They differ from elapids in being more lightly build overall, with much longer centra and prominent subcentral ridges. Despite the hypapophyses being presented as a definitive character for natricids as a whole, McDowell (1961), Malnate (1972), and Ikeda (2007) showed that there are a few exceptions to this rule outside of North America, possibly representing a loss of this character later in the evolution of some species.</p>
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	https://treatment.plazi.org/id/03B387E8FFBA321884E3F9EB9C63F9BE	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBB321F84D0F9A69A72FCE6.text	03B387E8FFBB321F84D0F9A69A72FCE6.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Neonatrix Holman 1973	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  NEONATRIX Holman, 1973 † </p>
            <p> Diagnosis.  Neonatrix trunk vertebrae are most easily characterized by very short hypapophyses that strongly project posteriorly, are ventrally beveled in most North American species (except  Neonatrix elongata ) but are weakly developed, terminally rounded, and do not extend beyond the end of the condyle. Furthermore, they are relatively small and distinctly longer than wide. The neural spines of  Neonatrix are much longer (up to 4x) than wide (Holman, 1973, 2000; Parmley and Hunter, 2010), with reduced or absent hooked projections at each terminal end. The zygosphene is convex, but less so in caudal vertebrae (Jasinski and Moscato, 2017). </p>
            <p> Remarks. The hypapophyses of North American species of  Neonatrix are less well-developed than the reported species from Europe (Holman, 1973, 1982, 1996; Rage and Holman, 1984) and shorter than in any other natricid genus (Holman, 1973, 2000).  Neonatrix also differs from  Thamnophis and  Nerodia in possessing an anteriorly taller neural spine that lacks hooked projections and a less prominant subcentral ridge (Jasinski and Moscato, 2017). The neural spine of  Neonatrix is also taller than in  Storeria ,  Tropidoclonion ,  Virginia , and  Micronatrix , but shorter than in  Seminatrix (Parmley and Hunter, 2010; Jasinski and Moscato, 2017) </p>
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	https://treatment.plazi.org/id/03B387E8FFBB321F84D0F9A69A72FCE6	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBC321E8650FC8E9DDFF9EC.text	03B387E8FFBC321E8650FC8E9DDFF9EC.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Neonatrix elongata Holman 1973	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Neonatrix elongata Holman, 1973 † </p>
            <p>Figure 10</p>
            <p>Material. UNSM 139986 (17 pre-cloacal trunk vertebrae).</p>
            <p> Description. The diagnosis follows that of Holman (2000) and is only modified where otherwise noted.  Neonatrix elongata trunk vertebrae are longer than wide, with a neural spine that is drastically longer than tall or wide. The vertebrae possess poorly developed hypapophyses reaching only the posterior portion of the centrum, and unbeveled neural spines that end just short of the posterior end of the cotyle. </p>
            <p>In anterior view, the neural canal is shaped like a ventrally restricted semi-cylinder, is medially convex at the sides, and is slightly narrower than the round cotyle. The zygosphene is convex dorsally. The synapophysis is developed. For the first time in this genus and species, we confirm the presence of paracotylar foramina in anterior view, adjacent to the cotyle on each side, approximately half-way down the cotyle. Previous descriptions exhibited excavated cavities on either side of the cotyle, but could not observe any foramina based on the specimens available.</p>
            <p>In dorsal view, the centrum is longer than wide. The prezygapophyseal articular facets are ovoid in shape. This is a correction of Holman (2000), which appears to have mistakenly labeled the prezygapophyseal processes as ovoid, rather than the articular facets. The prezygapophyseal processes are long and somewhat pointed on the anterior end. The diapophyses only slightly extend out laterally. The epizygapophysel spines are absent or obsolete.</p>
            <p> In lateral view, the vertebrae are elongate. The neural spine is over two times as long as it is high. The neural spine is rarely preserved at the ends in Penny Creek fossils and in  Neonatrix throughout the fossil record, and so is difficult to observe, but a few mostly preserved neural spines from Penny Creek material allow us to determine the absence of an anterior projection, and an extremely reduced to absent – typically absent – posterior overhang. The subcentral ridge is convex dorsally. The prezygapophyses tilt somewhat dorsally. The hypapophysis is short and ends short of the posterior-most part of the condyle; we find that it is does not extend past even the anterior-most part of that articulation in these specimens. </p>
            <p>In posterior view, we find that the condyle is near circular, but is slightly depressed and closer to an oval shape in some vertebrae. The neural arch is vaulted, steeply incised by the zygantral articular facets, and similar in size to the condyle. The hypapophysis is visible below the condyle around onehalf of the condyle’s height when undamaged. The postzygapophyses tilt slightly upward, just as in the prezygapophyses. In ventral view, the centrum is long and narrow. The subcentral grooves are shallow, and the hemal keel narrows slightly anteriorly to the robust but truncated hypapophysis.</p>
            <p> Remarks. Like other species of North American  Neonatrix ,  N. elongata have less well-developed hypapophyses that do not extend as far posteriorly (relative to the condyle) than found in the European species (Rage and Holman, 1984).  N. elongata occurs earlier than other North American species of  Neonatrix and is known to occur more broadly in a temporal and geographic manner throughout the Miocene. In the Penny Creek specimens, the unbeveled neural spine and unbeveled hypapophysis that end just short of the posterior end of the cotyle indicate that these fossils belong to  N. elongata , as opposed to other known species of  Neonatrix . There is some variation on how rounded (or pointed) the posterior tips of the hypapophyses are, likely indicating a small amount of intracolumnar variation in the hypapophyseal morphology of the species (LaDuke, 1991; McCartney, 2015). Nonetheless, we have not observed more variation within an individual taxon than between species, and the morphology is generally consistent with what is described above.  Neonatrix elongata is typically smaller than  Neonatrix magna and  Neonatrix infera , but the taxon’s relative length and neural spine height are intermediate between the other two species, which are either more elongate with a shorter neural spine (  N. infera ) or less elongate with a taller neural spine (  N. magna ; Holman, 2000). It is noteworthy that these specimens show some measure of variation in terms of the neural spine height and the shape of the hypapophyses, some of which appear similar to some morphologies known in the other North American species. Given that  N. elongata was considered to have “intermediate” morphologies by Holman (2000), it may be necessary to further study the intracolumnar variation with  Neonatrix for additional definitive characters and consider potential changes to the taxonomy of the species within. </p>
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	https://treatment.plazi.org/id/03B387E8FFBC321E8650FC8E9DDFF9EC	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBD321C84C2F9909D59FEFB.text	03B387E8FFBD321C84C2F9909D59FEFB.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Neonatrix magna Holman 1982	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Neonatrix magna Holman, 1982 † </p>
            <p>Figure 11</p>
            <p>Material. UNSM 139987 (8 pre-cloacal trunk vertebrae).</p>
            <p> Description. The diagnosis is based on that of Holman (2000) but is modified where noted. The vertebrae are mainly distinguished by (1) a very poorly developed hypapophysis that typically terminates near the posterior part of the centrum; (2) ventral portion of the hypapophysis beveled and ending well anterior to the condyle; (3) vertebral size relatively large (at least relative to other North American  Neonatrix at&gt; 5 mm); (4) vertebrae nearly the same width and length; and (5) neural spine near same height and length. </p>
            <p>In anterior view, the cotyle is round and similar in size to the neural canal, which is an inverted Ushape with slightly convex lateral sides. The zygosphene is dorsally straight. The prezygapophyses are slightly tilted dorsally. Short excavations with single, centered paracotylar foramen border each side of the cotyle. We observe that the synapophyses that are missing from previous descriptions are moderately well developed and differentiated.</p>
            <p>In dorsal view, the centrum’s length and width are similar. The prezygapophyses are ovoid. The neural spine is somewhat thick and slightly overhangs posteriorly when preserved. Epizygapophyseal spines are absent. The zygosphene is slightly convex anteriorly. The diapophyses are produced laterally enough to be seen from the dorsal orientation.</p>
            <p>In lateral view, the vertebra is only slightly elongate. The neural spines are not completely preserved but appear as though they are similar in height and length. There is a slight overhang on the posterior border of the neural spine. The hypapophysis is beveled ventrally, about as tall as it is long, and ends anterior to the condyle, but appears to have rounded rather than the pointed tips observed by Holman (1982; 2000).</p>
            <p>In posterior view, the neural arch is significantly vaulted. We observed that the condyle is mostly round and slightly compressed, rather than truly oval, and is similar in size to the neural canal. The hypapophyses strongly projects ventrally and is clearly visible below the condyle.</p>
            <p>In ventral view, the hypapophysis is somewhat narrow, ends clearly anterior to the anterior end of the condyle, and is beveled on the ventral surface. The subcentral ridges are well developed.</p>
            <p> Remarks.  Neonatrix magna has the shortest relative length and widest appearance, the highest neural spine, and most anteriorly terminating hypapophyses of any species of  Neonatrix in North America or Europe. It also has somewhat less strongly developed subcentral ridges and deep subcentral groups than  N. elongata or  N. infera . </p>
            <p> Several of our observations contribute to or differ slightly from previous descriptions of the species. We observe that the synapophyses are moderately developed. The hypapophyses of our specimens have rounded rather than pointed tips, and the condyle, while slightly depressed, is better described as round rather than oval. Comparison with specimens of  N. elongata and examination of intracolumnar differences in vertebral morphology in extant natricid snakes suggest that the hypapophysis does change shape along the column; however, the differences in the hypapophysis alone between the two species described from fossils seems to be greater than generally seen in other natricids, except between anterior or middle trunk vertebrae and precloacal vertebrae. Given other morphological differences discussed above and the observation that  N. magna is not smaller but would appear to have a morphology more similar to the smaller posterior trunk and precloacal vertebrae, we do not believe that these vertebrae represent the same species. Nonetheless, little is known about the intracolumnar variation of  Neonatrix at this time, as preserved elements are mainly trunk vertebrae; this would seem to warrant a more complete investigation, as also suggested by Jasinski and Moscato (2017). </p>
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	https://treatment.plazi.org/id/03B387E8FFBD321C84C2F9909D59FEFB	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
03B387E8FFBF321C84F2FEE99AAAF9AE.text	03B387E8FFBF321C84F2FEE99AAAF9AE.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Nerodia Baird and Girard 1853	<html xmlns:mods="http://www.loc.gov/mods/v3">
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            <p> Genus  NERODIA Baird and Girard, 1853</p>
            <p> Diagnosis. The trunk vertebrae of  Nerodia are typically medium to large in size and relatively short and wide, with an elongate centrum (Holman, 2000). The neural spines and hypapophyses are prominent (Holman, 2000). The neural spine is tall and undercut on both the anterior and posterior sides. The robust hypapophyses on each precaudal vertebra are well-developed, laterally compressed, directed posteriorly, and usually end in a somewhat pointed tip extending beyond the condylar head (Holman, 2000). Epizygapophyseal spines are absent (Holman, 2000). </p>
            <p> Remarks. The trunk vertebrae of  Nerodia relative to other North American natricids are typically medium to large in size, relatively robust in appearance, and exhibit higher neural spines (Holman, 2000). The vertebrae are still elongate relative to large North American colubrines (Holman, 2000).  Nerodia vertebrae are typically less elongate than  Thamnophis vertebrae, with a more ventrally-oriented hypapophysis with a steeper angle relative to the centrum (LaDuke, 1991; Holman, 2000; Jasinski and Moscata, 2017).  Nerodia also exhibits a more vaulted neural arch, broader and more robust hypapophyses, but more gracile prezygapophyses compared to  Thamnophis (Jasinski and Moscato, 2017) . They possess higher neural spines than  Storeria ,  Tropidoclonion , and  Virginia (but relatively shorter than  Regina ), and the hypapophyses are longer and less squared in shape when compared to  Regina (Holman, 2000) . It should be noted that the degree to which the hypapophysis extends beyond the condylar head appears to differ between some taxa, and perhaps between individuals, though this has not been extensively studied at this time. Other characters of  Nerodia , such as neural spine height, hypapophysis shape, and the degree to which the neural spine is undercut all vary to some degree at least between species of the genus (Holman, 2000; pers. obs.). </p>
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	https://treatment.plazi.org/id/03B387E8FFBF321C84F2FEE99AAAF9AE	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Jacisin Iii, John J.;Lawing, A. Michelle	Jacisin Iii, John J., Lawing, A. Michelle (2024): Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America. Palaeontologia Electronica (a 2) 27 (1): 1-42, DOI: 10.26879/1220, URL: http://dx.doi.org/10.26879/1220
