taxonID	type	description	language	source
1A3B87CCFFF7B47B07EAFDCC3C53FC2D.taxon	description	Eoalphadon clemensi MNA. V. 5387 M 2 Eoalphadon lillegraveni MNA. V. 5835 M 2 Eoalphadon woodburnei UMNH VP 12842 M 3 Protalphadon foxi UCMP 109031 M 3 Protalphadon lulli UCMP 47446 M 3 Protalphadon lulli UCMP 47475 M 3	en	Brannick, Alexandria L., Fulghum, Henry Z., Grossnickle, David M., Wilson Mantilla, Gregory P. (2023): Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians. Palaeontologia Electronica (a 48) 26 (3): 1-42, DOI: 10.26879/1177, URL: http://dx.doi.org/10.26879/1177
1A3B87CCFFF7B47707EAFC393AF7FDE3.taxon	description	Turgidodon praesagus UALVP 55849 M 3 Turgidodon praesagus UCMP 122168 M 3 Turgidodon praesagus UCMP 131345 M 2 Turgidodon rhaister UCMP 47366 M 2 Turgidodon russelli UALVP 55852 M 3 Turgidodon russelli UALVP 6983 M 3 Varalphadon creber UALVP 29525 M 3 Varalphadon creber UALVP 29527 M 3 Varalphadon creber UALVP 5529 M 3 Varalphadon UALVP 5544 M 3 wahweapensis Atokatheridium boreni OMNH 61623 M 2 Glasbius intricatus UCMP 102111 M 3 Glasbius twitchelli UCMP 153679 M 3 Glasbius twitchelli UCMP 156143 M 3 Glasbius twitchelli UCMP 224090 M 3 Nortedelphys intermedius UCMP 134776 M 3 Nortedelphys jasoni UCMP 174506 M 3 Nortedelphys jasoni UCMP 177838 M 3 Nortedelphys magnus UA 2846 M 3 Nortedelphys minimus UCMP 52715 M 2 Nortedelphys minimus UCMP 72211 M 3 Anchistodelphys archibaldi OMNH 21033 M 3 Apistodon exiguus UALVP 29693 M 3 Dakotadens morrowi OMNH 49450 Mx Alphadontidae Judithian cast Alphadontidae Judithian cast Alphadontidae Aquilan fossil Alphadontidae Aquilan fossil Alphadontidae Aquilan fossil Alphadontidae Judithian fossil Alphadontidae Lancian fossil Alphadontidae Lancian fossil Alphadontidae Judithian cast Alphadontidae Lancian fossil Alphadontidae pre-Aquilan fossil Alphadontidae pre-Aquilan cast Alphadontidae pre-Aquilan fossil Alphadontidae Lancian fossil Alphadontidae Lancian fossil Alphadontidae Lancian fossil Alphadontidae Judithian cast Alphadontidae Judithian cast Alphadontidae Judithian fossil Alphadontidae Judithian fossil Alphadontidae Judithian fossil Alphadontidae Lancian fossil Alphadontidae Judithian fossil Alphadontidae Judithian fossil Alphadontidae Aquilan fossil Alphadontidae Aquilan fossil Alphadontidae Aquilan fossil Alphadontidae Aquilan fossil Deltatheridiidae pre-Aquilan cast Glasbiidae Lancian fossil Glasbiidae Lancian fossil Glasbiidae Lancian fossil Glasbiidae Lancian fossil Herpetotheriidae Lancian fossil Herpetotheriidae Lancian fossil Herpetotheriidae Lancian fossil Herpetotheriidae Lancian cast Herpetotheriidae Lancian fossil Herpetotheriidae Lancian fossil incertae sedis Aquilan cast incertae sedis Aquilan fossil incertae sedis pre-Aquilan cast include in our sample any extant mammal species with teeth that have, to our knowledge, secondary wear-induced functionality. Specimens with cusps missing due to breakage were also excluded. Dietary Categories We classified each extant species in our dataset into one of six dietary categories: carnivory (carn), animal-dominated omnivory (ado), plant-dominated omnivory (pdo), frugivory (frug), invertivory (inv; i. e., ‘ insectivory’), or soft-invertebrate specialist (sis) (Table 2). We used six specific dietary categories rather than the classic three-diet classification scheme (herbivory-omnivory-carnivory) to provide more detailed dietary information and to avoid oversimplification (Pineda-Munoz and Alroy, 2014). Our choice of diet categories follows Smith (2017), who used these six categories (along with folivory and hard-object invertivory) in DTA analyses of lower molars. Our ‘ soft-invertebrate specialist’ group includes taxa that primarily consume soft invertebrates such as earthworms and slugs, whereas our ‘ invertivory’ (i. e., ‘ insectivory’) group includes taxa that primarily eat relatively harder-bodied insects, such as beetles and moths. Following Pineda-Munoz and Alroy (2014), we classified diets of each species, with emphasis on its primary food resource. A species was classified as a specialist (i. e., non-omnivore) if one food resource makes up 50 % or more of its total diet. For dietary information, we used online archives (EltonTraits [Wilman et al., 2014] and Mammal DIET [Kissling et al., 2014]) and a natural history compendia (Nowak, 1999). We supplemented each classification with primary literature sources (see Table 2 for sources), which were especially important when species-level information was extrapolated from genus-level information in the online archives (see Kissling et al., 2014; Table 2). We acknowledge that our decision to use six dietary categories rather than the classic ‘ carnivore-omnivore-herbivore’ trophic classification could lead to greater overlap of categories in the morphospace and less power to predict diet. We classified the diet of some extant taxa in our sample differently than previous studies have. For example, Nasua narica (white-nosed coati) is known to eat insects, but it is strictly frugivorous when fruit is available (e. g., Nowak, 1999). Although some studies classified its diet as plant-dominated omnivory (Smith, 2017), we followed EltonTraits, which records its diet as 70 % fruit and considered this taxon a frugivore. We recognize that in this and any large-scale study of mammalian feeding behaviors, decisions that reduce the complexity of dietary data into discrete categories could have an impact on the results. Fossil Metatherian Sampling We sampled 71 isolated upper molars of 42 species (22 genera; six major clades) of North American Late Cretaceous (NALK) metatherians from the Western Interior region (Table 3). Our sample includes two stagodontids, one deltatheriid, two glasbiids, eight pediomyids, six taxa classified as incertae sedis, four herpetotheriids, and 19 alphadontids. To increase our taxonomic sampling of Cretaceous metatherians, we substituted the M 2 (which tends to be morphologically very similar to the M 3) for some species that did not have an available M 3, and we used upper molar specimens of uncertain position (i. e., “ Mx ”) for some species that did not have definitive M 2 or M 3 specimens available (see Table 3 for details). Our sample includes 62 % of the known species of NALK metatherians (42 of 68 known species; Case et al., 2005; Williamson et al., 2014; Cohen, 2018; Cohen et al., 2020). Some species were omitted from our sample because of either a lack of a well-preserved upper molar in the fossil record or an appropriate specimen was not available for loan. Our sampling of deltatheriids and stagodontids is limited, and this likely artificially reduced both morphological disparity values and morphospace occupation (e. g., Nanocuris has been interpreted as a specialized carnivore), especially in the pre-Aquilan and Lancian time bins (see below). The absence of other taxa may have had a negligible effect on the results because their morphologies are approximated by other sampled taxa (e. g., the absence of the pediomyoid genus Aquiladelphis may be accounted for by the presence of other pediomyoid genera in our sample to some degree). We assigned each fossil species in our sample to one (or more) of four time bins depending on the known temporal range of each species (Williamson et al., 2014), using a range-through approach. Three bins are Cretaceous NALMAs (Woodburne, 2004): Aquilan (ca. 86 – 79 Ma), Judithian (79 – 69 Ma), and Lancian (69 – 66 Ma). We binned the eight specimens from geologic units that pre-date the Aquilan NALMA into a “ pre-Aquilan ” time bin (ca. 126 – 86 Ma). Most taxa that we assigned to the pre-Aquilan time bin are from 100 – 86 Ma, but we also include Atokatheridium, which has a range of ca. 126 – 100 Ma. Because the “ Edmontonian ” NALMA is poorly characterized and not well sampled (Cifelli et al., 2004), we lumped the “ Edmontonian ” taxa into the Judithian bin. We recognize that these time bins are uneven in duration and that the longer duration bins could artificially inflate measures of disparity and diversity; however, we were unable to more finely and precisely bin our data due to uneven sample sizes across time bins and the lack of high-precision ages for certain geologic units. Collection of 3 D Tooth Surface Data Three-dimensional digital models of the sampled teeth were created using micro-computed tomography (μCT) scan data. We scanned original specimens of teeth, molds of teeth, and epoxy casts of teeth (Tables 2 – 3). López-Torres et al. (2017) found that OPCR values of epoxy casts tend to be higher than those from their original specimens due to potential for artificially rougher surfaces on the casts (both DNE and RFI are more robust to this effect). Thus, we interpret OPCR results for the relatively few casts in our sample (15 of 71 specimens) with caution. Specimens were scanned using either a Bruker Skyscan 1172, Skyscan 1173, or NSI X 5000 scanner, all of which are housed on the University of Washington campuses. We also downloaded image stacks (TIFF format) of scan data for eight extant specimens (Table 2) from the MorphoSource online repository (morphosource. org) to bolster our modern comparative dataset (Appendix 1). For detailed information regarding scanner types and scan settings, see Appendix 2. Molds of extant teeth were made using Coltene President Plus polyvinylsiloxane (type 2, medium consistency), and epoxy casts were collected from the UWBM, University of California Museum of Paleontology, and Sam Noble Oklahoma Museum of Natural History collections. For specimens scanned with Bruker Skyscan scanners, scan data were reconstructed using NRecon (Bruker microCT, Belgium); scans completed using the NSI X 5000 were reconstructed using efX Reconstruction (North Star Imaging, Inc.). We segmented raw scan data using Avizo Lite 9.2.0 (Thermo Fisher Scientific). We then removed artifacts (“ cleaning ”), cropped, and oriented tooth models using GeoMagic Studio (3 DS Systems). Specimen models were cropped to include the entire enamel cap (EEC cropping method; see Berthaume et al., 2019 for details) and were oriented such that the occlusal plane is perpendicular to the Z-axis. We exported the cleaned and oriented 3 D tooth models from GeoMagic Studio as PLY files. These PLY files were imported back into Avizo Lite 9.2.0, and the 3 D tooth models were simplified to 20,000 faces using the Simplification Editor tool. We then used the “ Remesh Surface ” function to downsample the tooth models to ~ 10,000 faces. The remesh function was used because it reduces the chance that surfaces with extremely disparate polygon mesh face-sizes are produced during simplification (Spradley, personal comm., 2018). We then used the “ Smooth Surface ” function with 25 iterations and lambda = 0.6 (Spradley et al., 2017; Spradley, personal comm., 2018). Because the consistency of model creation and processing is extremely important for producing comparable DTA results (Spradley et al., 2017; Berthaume et al., 2019), we used the same workflow for the creation of all models in this study. The resulting smoothed tooth models were saved as PLY files and used in our DTA analyses. Dental Topographic Analyses (DTA) We computed RFI, DNE, and OPCR for all 3 D tooth models using the molaR _ Batch function from the package molaR, version 4.2 (Pampush et al., 2016), in R version 3.3.3 (R Core Team, 2017). RFI is the ratio between the 3 D surface area of a tooth crown and the 2 D “ footprint ” area of a tooth (Ungar and M’Kirera, 2003). We use a modified version of this ratio in which the entire tooth crown is more accurately considered (Boyer, 2008). The modified RFI calculation is: (A 3 D = 3 D embedded surface area of the tooth crown, A 2 D = 2 D tooth crown footprint area in occlusal view; Boyer, 2008; López-Torres et al., 2017). DNE represents the curvature of the tooth crown by calculating the sum energy values across the entire occlusal surface (Bunn et al., 2011; Winchester et al., 2014; Winchester, 2016). OPCR measures tooth crown complexity by calculating the total number of patches, or “ tools, ” on the crown of a tooth. A patch is a contiguous group of pixels that face the same cardinal direction on the tooth model (Evans et al., 2007; Evans and Jernvall, 2009; Wilson et al., 2012). Parameters for each metric were set as follows: RFI — alpha = 0.15; DNE — boundary discard = “ Vertex ”; and OPCR — step size = 8 and minimum patch size = 3 pixels (Evans et al., 2007; Pampush et al., 2016; Smith, 2017; Spradley, 2017). We ran a second DTA with the OPCR minimum patch size = 5 pixels to minimize any “ noise ” that might artificially inflate values for our extant and fossil samples, which include molds and casts, respectively (Winchester, 2016; López-Torres et al., 2017). We log-transformed our DTA data to reduce skew. We generated scatter biplots of all possible combinations of the dental metrics to visualize morphospace occupation of extant dietary groups. We then plotted our fossil metatherian DTA values within the same morphospace of the extant dataset to examine both how fossil morphospace occupation compared to extant mammal morphospace occupation and how fossil morphospace occupation changed through time. We also tested for correlation between our DTA metrics by calculating Spearman’s rho and using least-squares linear regressions. To test for differences between DTA values of the six dietary groups, we used one-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) post hoc test. We also performed a MANOVA using all three DTA metrics as independent variables. Dietary Inference of Fossil Metatherians To quantitatively infer diet in our sample of fossil metatherians, we conducted a discriminant function analysis (DFA) using the function lda () from the package MASS (Venables and Ripley, 2002). We first used the extant comparative dataset and a leave-one-out cross validation to assess the accuracy of discriminant functions in predicting diet (see MASS package documentation for more information). We then applied this DFA to the fossil metatherian DTA data (with fossils treated as having unknown diets), and we used posterior probabilities of dietary groupings to infer fossil diets. In a second permutation, we conducted a DFA on the extant comparative dataset using both the DTA data and mean body mass (compiled from the primary literature) to test whether this would significantly improve the discriminatory power of our model (Winchester et al., 2014). Because the resulting accuracy did not significantly improve discrimination, we only report the results from the first permutation. For fossil species in which different specimens were classified differently by the DFA (e. g., Didelphodon vorax), we based our dietary inferences on additional evidence, such as which diet was most commonly reconstructed by the specimens and evidence from previous studies, or we simply report two possible diet classifications for the species. Dental Disparity of Fossil Metatherians We calculated morphological disparity in our sample of fossil metatherians as: i) intra-family disparity and ii) total disparity per time bin. We did not calculate the intra-family disparity per time bin because sample sizes were too small. All disparity calculations used mean species values of each standardized, log-transformed DTA metric. We measured disparity as both the variance of each DTA metric and the sum of variances (Ciampaglio et al., 2001) using the morphol. disparity function in the geomorph package in R (Adams et al., 2020), which calculates a simulation-based P - value for statistical comparison between groups (i. e., between families or between time bins). We generated 95 % confidence intervals using a custom bootstrapping function in R with 1,000 replicates. Testing for Phylogenetic Signal We tested for phylogenetic signal in the DTA results of our extant comparative dataset using a phylogenetic tree that we generated suing TimeTree (www. timetree. org; Kumar et al., 2017). We calculated Blomberg’s K (Blomberg et al., 2003) and Pagel’s lambda (Pagel, 1992) using the phylosig function in the package phytools in R (Revell, 2012). We did not test for phylogenetic signal in the DTA results of our fossil taxa because the most recent species-level phylogeny that includes all of the fossil taxa in our sample (Williamson et al., 2014) is highly unresolved with a large polytomy.	en	Brannick, Alexandria L., Fulghum, Henry Z., Grossnickle, David M., Wilson Mantilla, Gregory P. (2023): Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians. Palaeontologia Electronica (a 48) 26 (3): 1-42, DOI: 10.26879/1177, URL: http://dx.doi.org/10.26879/1177
1A3B87CCFFE0B46C07F6FBCE3C7DFAA2.taxon	description	Eptesicus fuscus UWBM 66980 inv - Eptesicus fuscus UWBM 79331 inv - Lynx rufus OUVC 9576 carn -	en	Brannick, Alexandria L., Fulghum, Henry Z., Grossnickle, David M., Wilson Mantilla, Gregory P. (2023): Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians. Palaeontologia Electronica (a 48) 26 (3): 1-42, DOI: 10.26879/1177, URL: http://dx.doi.org/10.26879/1177
1A3B87CCFFE0B46E07F6F8EE3A00FEF7.taxon	description	0.006 0.009 - 0.727 0.256 - - - 0.455 * 0.545 0.098 0.428 * - 0.003 0.001 0.096 0.463 - 0.001 - 0.059 0.254 0.011 0.001 0.001 0.344 0.251 * 0.008 0.156 0.194 0.576 0.298 0.015 - - 0.216 0.321 0.020 - - 0.182 0.305 0.001 - - 0.174 0.138 0.514 - 0.001 0.671 0.147 0.148 - 0.002 0.010 0.002 0.985 - 0.002 0.266 0.199 0.140 0.056 0.265 * 0.469 0.293 0.051 0.027 0.079 0.169 0.382 * 0.004 0.001 0.001 0.320 * 0.346 0.014 - - 0.427 * 0.434 0.001 0.006 0.003 0.386 * 0.420 0.007 0.014 0.014 0.444 0.390 * 0.007 0.002 0.002 0.076 0.096 0.444 - - - - - 0.723 0.276 - - - 0.827 0.173 - - - 0.730 0.269 - - 1.000 - - 0.152 0.294 0.013 - - 0.210 0.439 0.001 0.001 0.001 0.335 0.279 * 0.014 - - 0.149 0.078 0.002 0.384 0.380 * 0.363 0.243 0.179 - - 0.127 0.195 0.216 - - 0.008 0.018 - 0.682 0.287 0.017 0.176 0.007 0.017 0.014 0.484 0.366 0.009 0.001 0.002 0.081 0.030 0.317 0.033 0.532 0.258 0.390 0.017 0.002 0.003 0.497 0.315 0.050 0.001 0.004 0.295 0.417 0.014 0.025 0.031 0.071 0.097 0.041 0.189 0.554 0.125 0.398 * 0.005 0.013 0.009 upper and lower molars, it is likely due to the idiosyncrasies of our carnivore sample. Two of the six carnivore taxa (Crocuta crocuta, the spotted hyena and Sarcophilus harrisii, the Tasmanian devil) are known for their bone-cracking / durophagous habits (e. g., Werdelin, 1989; Wroe et al., 2005), and another taxon (Eira barbara, the tayra) supplements its carnivorous diet with fruit and honey (Bisbal, 1986). Increasing the sampling of hypercarnivorous taxa may add clarity to DTA patterns for carnivores and subsequent DFA carnivore classifications. Additionally, the DNE and OPCR values of our frugivore sample differ from those of previous studies: they are slightly higher and more variable (Bunn et al., 2011; Winchester et al., 2014). This discrepancy also likely reflects differences in taxon sampling. Whereas previous studies heavily sample primate frugivores, our sample includes one primate and four other taxa from Chiroptera, Carnivora, and Cetartiodactyla. Most of these other taxa incorporate small amounts of foods besides fruit into their diet (e. g., Pecari tajacu, the collared peccary, incorporates roots, insects, and small vertebrates in addition to fruit [Nowak, 1999; Desbiez et al., 2009]). The higher DNE and OPCR values in our frugivore sample may reflect dental adaptations, such as rugosities, for processing these other food materials (Santana et al., 2011; Smith, 2017), or other specialized features for processing poorly documented fallback foods (food consumed less often but are critical for survival during times of environmental stress) — an example of Liem’s paradox (e. g., Ungar, 2010). The DFA correctly classified extant invertivores and soft-invertebrate specialists at the highest rate among the diet categories (Table 8). The few misclassified invertivore specimens were classified as soft-invertebrate specialists and vice versa. The DFA did not predict animal-dominated omnivores as reliably; some specimens were misclassified as frugivores, plant-dominated omnivores, and one as an invertivore. Among the frugivore sample, two specimens were misclassified as plant-dominated omnivores, one as a carnivore, and one as an animal-dominated omnivore. Among the plant-dominated omnivore sample, one specimen was misclassified as an animal-dominated omnivore and one as a frugivore. Often the assigned diet had the second highest posterior probability. These misclassifications likely stem in part from the overlapping range of DTA values among these dietary categories (Figures 2 – 3), which perhaps reflects some combination of dental morphological convergence among some animals in our extant sample, the incomplete and variable quality of the dietary data available, and the imperfect nature of the diet categorizations. There were nine instances in which multiple specimens of the same extant species were classified into different dietary categories by the DFA and Species Specimen pred. diet frug pdo ado carn inv sis	en	Brannick, Alexandria L., Fulghum, Henry Z., Grossnickle, David M., Wilson Mantilla, Gregory P. (2023): Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians. Palaeontologia Electronica (a 48) 26 (3): 1-42, DOI: 10.26879/1177, URL: http://dx.doi.org/10.26879/1177
1A3B87CCFFE2B46607D0F8FE3B65FCEE.taxon	description	- - - 0.002 0.027 0.001 0.004 - 0.028 0.019 0.093 0.002 0.015 0.011 0.027 0.073 - 0.020 0.002 0.003 0.021 0.026 0.026 0.001 0.002 0.004 0.006 0.013 0.203 0.156 0.103 0.131 0.005 0.030 0.004 0.002 0.017 0.001 0.004 0.002 - 0.529 0.466 * 0.005 0.004 - 0.725 0.266 0.006 0.004 - 0.799 0.191 0.012 0.008 - 0.692 0.288 0.026 0.021 - 0.671 0.280 0.435 0.185 0.029 0.086 0.239 0.010 0.008 - 0.770 0.211 0.060 0.042 - 0.564 0.330 0.001 0.001 - 0.846 0.153 0.375 0.195 0.013 0.137 0.251 0.192 0.115 0.014 0.211 0.450 0.442 0.394 * 0.003 0.038 0.029 0.044 0.029 - 0.611 0.314 0.403 0.141 0.020 0.113 0.307 * 0.292 * 0.121 0.005 0.225 0.346 0.349 0.156 0.055 0.086 0.328 * 0.444 0.291 0.033 0.048 0.112 0.003 0.002 - 0.815 0.180 0.171 0.120 0.006 0.282 0.401 0.037 0.031 - 0.724 0.205 0.159 0.049 0.004 0.259 0.526 0.236 0.145 0.006 0.249 * 0.343 0.227 * 0.169 0.003 0.298 0.277 * 0.312 0.181 0.008 0.196 0.278 * 0.011 0.009 - 0.669 0.311 0.022 0.016 - 0.530 0.430 * 0.070 0.044 0.001 0.515 0.367 0.068 0.044 0.002 0.370 0.510 0.128 0.061 0.118 0.082 0.597 0.388 0.375 * 0.027 0.002 0.005 0.397 0.251 0.193 - 0.003 0.436 0.383 * 0.007 0.034 0.037 0.435 0.331 * 0.060 0.011 0.032 0.073 0.044 0.003 0.358 0.518 0.312 0.189 0.010 0.180 0.279 * 0.073 0.039 0.001 0.423 * 0.460 0.021 0.017 - 0.567 0.393 0.170 0.141 0.001 0.446 0.226 0.013 0.013 - 0.706 0.267 nine instances in which specimens of the same extinct species were classified differently from one another (Tables 9 – 10). In seven out of nine cases of the extant species, slight differences in wear among the specimens may have led to the different dietary assignments. In the other two cases, we did not detect differences in the amount of wear between the specimens of the same species. In both those cases, one specimen was classified as an invertivore and the other as a soft-invertebrate specialist, highlighting the substantial overlap in morphospace of these two invertebrate-eating diets (Figure 3). Thus, we highlight the need for further standardization and ground truthing of DTA methods. We recommend that whenever possible, studies should attempt to account for intraspecific variation by sampling more than one specimen per species and by controlling for wear across and within taxa. Dietary Inferences and Dietary Diversity of NALK Metatherians Although most Mesozoic mammals have conventionally been portrayed as small-bodied, terrestrial invertivores (e. g., Van Valen and Sloan, 1977; Kielan-Jaworowska et al., 2004), recent fossil discoveries and ecomorphological analyses have provided counterexamples, both among non-therians and therians, implying a much broader range of ecologies (e. g., Luo, 2007; Wilson et al., 2012; Grossnickle and Polly, 2013; Chen et al., 2019; Grossnickle et al., 2019). Our quantitative study of dental ecomorphology in part reinforces the conventional view by reconstructing most NALK metatherians (81 %, 34 of 42 species) as either invertivores or soft-invertebrate specialists (Tables 10, 12; Figure 6). These results are consistent with previous inferences from other studies using other methods (Gordon, 2003; Wilson, 2013; Williamson et al., 2014; Grossnickle and Newham, 2016) and with the observation that the most taxonomically rich families of Cretaceous metatherians (e. g., alphadontids and pediomyids) have conservative tribosphenic molar morphologies. Nevertheless, our DFA diet reconstructions predicted that a few NALK metatherians had diets beyond invertivory, indicating that NALK metatherians as a whole achieved greater dietary diversity than is conventionally portrayed. For example, our DFA reconstructed Glasbius as a plant-dominated omnivore, a prediction that is in line with previous interpretations that this taxon was either herbivorous or frugivorous (Clemens, 1966, 1979; Gordon, 2003; Kielan-Jaworowska et al., 2004; Wilson, 2013; Williamson et al., 2014). Overall, we see evidence of the following diets in NALK metatherians: invertivory, carnivory, animal- and plant-dominated omnivory (including durophagy), and likely frugivory. Dietary predictions for several taxa in our study conflicted with diet inferences from previous studies. In each case, however, the diet classification with the second highest posterior probability in our DFA matched with previous diet inferences. These taxa and their alternative diet classifications include (i) Iugomortiferum thoringtoni as a plant-dominated omnivore, (ii) Apistodon exiguus as an invertivore, and (iii) Alphadon halleyi, Alphadon wilsoni, and Protalphadon foxi as soft-invertebrate specialists. Below we discuss the diet reconstructions of these taxa in more detail. Seven taxa (Pariadens kirklandi, Eoalphadon lillegraveni, Apistodon exiguus, Alphadon halleyi, Alphadon wilsoni, Turgidodon lillegraveni, Protalphadon foxi) were reconstructed in our DFA as plant-dominated omnivores. Most of these taxa lack most of the gross morphological features (e. g., large talonid basin, large protocone, bunodont cusps) characteristic of the crushing and grinding function necessary for most plant-based diets. Instead, most of these taxa have the conservative tribosphenic molar morphology (e. g., sharp shearing crests and unexpanded protocones) that is typically found among invertivores (e. g., Cifelli, 1990; Johanson, 1996; Davis, 2007; Williamson et al., 2014; Cohen, 2018). Such discrepancies between our diet reconstruction and those from previous studies are expected, considering the difficulty that the DFA model had in correctly predicting animal-dominated omnivory, and to a lesser extent, plant-dominated omnivory, frugivory, and carnivory. For Pariadens kirklandi, Eoalphadon lillegraveni, and Turgidodon lillegraveni, the second highest posterior probabilities were for the animal-dominated omnivore category, and posterior probabilities of other dietary categories were much lower (Table 10); this provides additional evidence for omnivory despite the dearth of supportive qualitative evidence. We consider there to be less overall evidence of omnivory for Apistodon exiguus, Alphadon halleyi, Alphadon wilsoni, and Protalphadon foxi; instead invertivore or soft-invertebrate specialist may be a more plausible diet reconstructions for these taxa. Evidence for Apistodon exiguus being an invertivore includes its very small body size, previous interpretations of its gross dental morphology (Williamson et al., 2014), and invertivory having the second highest posterior probability for this taxon in our DFA. The interpretations of Alphadon halleyi and Alphadon wilsoni as soft-invertebrate specialists are in line with analyses of the jaw morphology (Grossnickle and Polly, 2013; Brannick and Wilson, 2020; Morales-García et al., 2021), gross dental morphology (Gordon, 2003; Wilson, 2013; Grossnickle and Newham, 2016), and the DFA results, in which the soft-invertebrate specialist category has the second highest posterior probability for both of these species. Evidence for P. foxi as a soft-invertebrate specialist includes its dietary classification in a similar DTA study on lower molars (Smith, 2017) and our DFA results, in which the soft-invertebrate specialist category has the second highest posterior probability (within 0.10 of the highest posterior probability) for this taxon. Thus, we consider Apistodon exiguus, Alphadon halleyi, Alphadon wilsoni, and Protalphadon foxi to likely have had insect-dominated diets, but the DTA and DFA results indicate that their diets also had a plant component; this is consistent with the view of the ancestral tribosphenic molar morphology being adapted for consuming both animal and plant materials (Butler, 1972). Our DFA reconstructed different diets for the two specimens of the relatively large-bodied Didelphodon vorax; one specimen as an invertivore and one as an animal-dominated omnivore. We favor the animal-dominated omnivore classification because it is in line with previous interpretations that D. vorax was a predator-scavenger with durophagous capabilities (Clemens, 1966, 1968, 1979; Fox and Naylor, 1986, 2006; Wilson et al., 2016; Brannick and Wilson, 2020) or an omnivore as indicated by dental microwear (Wilson et al., 2016). The bulbous premolars of Didelphodon are well suited for crushing hard objects, like bone and shells (Clemens, 1966; Fox and Naylor, 1995, 2006; Wilson et al., 2016; Cohen, 2018). One possible explanation for the invertivore reconstruction of one specimen is that we used relatively unworn molars (earlier ontogenetic wear stage) of Didelphodon in our analysis. That is, Didelphodon and other stagodontids may have experienced an ontogenetic shift in diet that tracks body size (Fox and Naylor, 1995, 2006; Peng et al., 2017) with younger individuals having been more faunivorous (e. g., molars with enhanced postvallum / prevallid shear and dentary shapes more capable of withstanding dorsoventral bending forces) and older individuals having been omnivorous / durophagous (e. g., horizontally worn grinding platforms and dentary shapes more capable of withstanding mediolateral forces; Fox and Naylor, 1995, 2006; Peng et al., 2017; Brannick and Wilson, 2020). Moreover, having analyzed only molar morphology, we did not account for critical dietary data from other tooth positions, such as premolars (Wilson, 2013; Smith, 2017). We suggest that future studies more deeply explore potential biases by comparing dietary inferences from DTA on a single tooth position to those from larger functional units like cheek tooth rows (Evans et al., 2007; Wilson et al., 2012). In a similar manner, further study of tooth wear as it relates to ontogenetic stage, functional efficiency, and dietary preference could lend important nuance to the dietary characterization of extinct taxa in studies using DTA (Ungar, 2010). Another productive line of inquiry for other taxa would be to compare dietary inferences from DTA to those from other quantitative methods that are independent of gross morphology of teeth (e. g., microwear, isotopic analyses, mandibular bending strength), as has been done for Didelphodon (Wilson et al., 2016; Brannick and Wilson, 2020). Although our DFA classified Iugomortiferum thoringtoni as a carnivore, this taxon has lowcrowned molar morphology with inflated cusps and weakly developed conules (Cifelli, 1990), all of which is inconsistent with interpretation of carnivory (de Muizon and Lange-Badré, 1997). The DNE value of I. thoringtoni is within the range of extant carnivores, plant-dominated omnivores, and frugivores, whereas its RFI value is within the range of extant carnivores, plant-dominated omnivores, and invertivores. Further, its low OPCR value is within the range of extant carnivores and invertivores. The OPCR value of I. thoringtoni may be underestimated because we used an epoxy cast of the specimen (OMNH 20936) and the small size of the specimen might have amplified any infidelities of the cast (although see discussion of cast fidelity and OPCR values in López-Torres et al., 2017). In addition, we analyzed only one specimen of I. thoringtoni, which has some wear and an uncertain identification of its position in the molar series (“ M 1? ” in Cifelli, 1990). Taking these considerations into account, we consider it very likely that I. thoringtoni was a plant-dominated omnivore rather than a carnivore, and further studies are needed to resolve this issue. Metatherian Ecomorphology through the Late Cretaceous By the beginning of the Late Cretaceous (ca. 100 Ma) metatherians in North America had diversified into at least four clades (Deltatheriidae, Stagodontidae, Aquiladelphidae, Alphadontidae, and possibly Glasbiidae, Pediomyidae, and Marsupialia were also present, see Wilson et al., 2016). This higher-level taxonomic diversification was associated with moderate dietary diversity — three of the six dietary categories that we recognize here (plant-dominated omnivory, invertivory, and soft-invertebrate specialists; Figure 6; Tables 10, 12). Raw species richness peaked in the Judithian (32 recognized species) and stayed relatively high in the Lancian leading up to the K-Pg mass extinction (22 species), although this peak might shift earlier in time or flatten if we account for differential sampling intensity through the Late Cretaceous (e. g., Grossnickle and Newham, 2016; Cohen, 2018; Bennett et al., 2018; Cohen et al., 2020). Nevertheless, according to our results, dental ecomorphological disparity did not significantly change throughout the Late Cretaceous and only in the Lancian did ecomorphological diversity (number of diet categories) increase slightly to include animal-dominated omnivory (Figures 5 – 6). Indeed, over 80 % of the taxa sampled (34 of 42) were interpreted as either invertivores or soft-invertebrate specialists (Table 12; Figure 6). A literal reading of our results would thus suggest that ecomorphological diversity and disparity did not track increases in taxonomic richness of NALK metatherians. This decoupled pattern has also been found in other taxonomic groups, such as anomodont therapsids (Ruta et al., 2013), graptoloids (Bapst et al., 2012), and angiosperms (e. g., Wing and Boucher, 1998; Lupia et al., 1999). That said, we caution that additional sampling might change this pattern. We were unable to sample several important stagodontids, including the middle Turonian (pre-Aquilan) Hoodootherium, and Fumodelphodon, the Aquilan through possibly “ Edmontonian ” Eodelphis, and Judithian and “ Edmontonian ” members of Didelphodon. These taxa, which have previously been interpreted as carnivores and animal-dominated omnivores (e. g., Scott and Fox, 2015; Cohen, 2018; Brannick and Wilson, 2020), would have likely pushed back the appearance of those diet categories and increased disparity values earlier in the Late Cretaceous. The Lancian deltatheriid Nanocuris, which has also been considered carnivorous on the basis of its distinctive, sectorial molars with carnassial notches (Fox et al., 2007; Wilson and Riedel, 2010), would have further added to the range of Lancian ecomorphologies and would have likely increased disparity values. We also did not sample the middle Turonian Scalaridelphys and Aquilan Aquiladelphis, respectively, both of which are pediomyoids that have both been interpreted as plant-dominated omnivores (Cohen et al., 2020). Thus, we underscore that our results should be taken as minimum estimates both for the magnitude of dietary diversity and dental ecomorphological disparity achieved by NALK metatherians and for when they achieved it. The oldest known dental fossils of metatherians, which date to ca. 110 Ma (Davis et al., 2008; Davis and Cifelli, 2011 and see Williamson et al., 2014; Bi et al., 2018 for discussion regarding Sinodelphys szalayi and the earliest eutherians), strongly suggest that invertivory was plesiomorphic for the clade (e. g., Williamson et al., 2014; Grossnickle and Newham, 2016). Together, our dietary inferences and those for the taxa that we were not able to sample indicate that by the early Late Cretaceous (ca. 100 Ma) metatherians were exploiting other food sources beyond insects (Cohen, 2018; Cohen et al., 2020). Notably, the dietary shifts toward omnivory (plant-dominated and animal-dominated omnivory) and carnivory largely occurred in metatherian subclades other than the most taxonomically prolific clades (the Alphadontidae and Pediomyidae) (Figure 6). Plant-dominated omnivory first appeared by the late Cenomanian (ca. 96 Ma) in the Stagodontidae (Pariadens kirklandi) and possibly Aquiladelphidae (Dakotadens morrowi, see discussion of phylogenetic relationships in Cohen et al., 2020). Later in the middle Turonian, stagodontids began their more thorough exploration of the carnivore and animal-dominated omnivore regions of the dietary ecomorphospace, culminating in the Lancian with the relatively large-bodied, durophagous predator-scavenger Didelphodon vorax. Glasbiidae is another group that shows up in the fossil record only at the very end of the Cretaceous (last 300 – 500 ky; Wilson, 2005); this sister taxon to Pediomyidae has only two known species (Glasbius twitchelli and Glasbius intricatus), but they are the most morphologically distinctive examples of plant-dominated omnivory-frugivory among NALK metatherians. Finally, deltatheroidans were likely the most carnivorous among the NALK metatherians, culminating in the highly specialized, Lancian carnivore Nanocuris (Fox et al., 2007; Wilson and Riedel, 2010). (Note that some Aptian – Albian members with a relatively larger talonid and a less reduced metaconid likely had diets other than strict carnivory [Rougier et al., 2015].) Nevertheless, the two most taxonomically rich clades of NALK metatherians, the Alphadontidae and Pediomyidae, show relatively little dietary diversity (Figure 6). Alphadontids originated by at least the Cenomanian (but probably earlier; Wilson et al., 2016) and peaked in taxonomic richness in the Judithian (15 species, including alphadontids not sampled here). The oldest known pediomyids are from the middle Turonian (Cohen et al., 2020), but like alphadontids, probably originated earlier and reached their highest taxonomic richness in the Judithian (five species, including pediomyids not sampled here) and sustained that level through the Lancian. Many of these alphadontid and pediomyid species were sympatric; for example, Protalphadon lulli, Alphadon marshi, Alphadon wilsoni, Turgidodon rhaister, Pediomys elegans, Leptalestes cooki, Leptalestes krejcii, Protolambda florencae, and Protolambda hatcheri are all found in the Lance Formation (see Williamson et al., 2014 for a tabulation of species occurrences per locality). Although previous studies have hypothesized that pediomyids had greater crushing and grinding capacity relative to other metatherian groups and, in turn, likely incorporated more plant material into their diets (Wilson, 2013; Cohen et al., 2020), our DFA shows that both pediomyids and alphadontids fed on mainly insects. Diet partitioning within the invertivore adaptive zone may help explain how alphadontids and pediomyids were able to maintain their tremendous taxonomic richness (e. g., eight species in the Hell Creek fauna) (Hardin, 1960). As more pediomyid taxa appear in the Judithian, alphadontids appear to experience a dietary shift from invertivory to soft-invertebrate specialization, whereas pediomyids were mostly invertivores (Table 12; Figure 6). It is possible that further dietary differences, such as specialization for particular species of insects, drove the niche partitioning, but that level of diet specificity cannot be detected by the methods utilized here. Other potential explanations of niche or resource partitioning include spatial separation (using different habitats), temporal avoidance, or separation along an ecological axis different from diet, such as locomotor mode or body size (e. g., Schoener, 1975; Keddy, 1989). For example, the two pediomyid species Protolambda florencae and Pediomys elegans are contemporaneous (Lance and Hell Creek faunas) and were both reconstructed by our DFA as invertivores. Resource partitioning may have occurred along the axis of body size (i. e., P. florencae is larger and so probably consumed larger insects than did Pediomys elegans), which might have enabled these pediomyids to co-exist. However, other potential ecological axes on which partitioning might have occurred are difficult to discern in this fossil record (e. g., locomotion / substrate use, diel activity pattern, etc.). During the Late Cretaceous in North America, metatherians shared the ecospace with other mammalian groups, including eutriconodontans, multituberculates, spalacotherioids, and their sister taxon eutherians. Among those groups, metatherians were arguably the most dietarily diverse, having occupied up to five categories: invertivory, carnivory, animal- and plant-dominated omnivory, and likely frugivory. It has been suggested that the non-tribosphenic dentitions of most non-therian mammals were more morphologically constrained than tribosphenic dentitions were, and, consequently, non-therians attained less dietary diversity than therians did (Chen et al., 2019; but see Harper et al., 2019 on South American dryolestoids). For instance, spalacotherioids and eutriconodonts were likely restricted to invertivory and faunivory, respectively (Hu et al., 2005; Grossnickle and Polly, 2013; Chen et al., 2019; Morales-García et al., 2021). Multituberculates were the most dietarily diverse non-therian mammal group. Their diets ranged from invertivory to animal- and plant-dominated omnivory, and by the late Late Cretaceous (ca. 84 Ma) even herbivory (Wilson et al., 2012; Grossnickle and Polly, 2013; Weaver et al., 2019; Weaver and Wilson, 2021). Still, metatherians probably had a broader dietary range than multituberculates and attained that diversity earlier in the Cretaceous. However, unlike multituberculates, metatherians did not continue to diversify in North America after the K-Pg mass extinction (Wilson, 2014; Williamson et al., 2014). The early eutherians, which include many lineages that retain the plesiomorphic tribosphenic molar morphology, were mostly insectivorous during the Late Cretaceous, although some of the larger-bodied taxa, such as Altacreodus magnus (formerly Cimolestes magnus), were likely faunivorous (e. g., Wilson, 2013; Grossnickle and Newham, 2016; Chen et al., 2019). Additionally, zhelestid (Harper, 2012; Gheerbrant and Astibia, 2012; Harper et al., 2019) and gypsonictopid eutherians (Crompton and Kielan-Jaworowska, 1978), which both first appear in North America in the Campanian, and the Lancian taeniodont Schowalteria (Fox and Naylor, 2003) are inferred to have included plant material in their diets based on their tooth morphology. Archaic ungulates, which first appear in the very latest Cretaceous but very rarely, and plesiadapiform primates, which have lineages that are believed to extend back into the very latest Cretaceous, have both been interpreted as animal- and plant-dominated omnivores (e. g., Archibald et al., 2011; Fox and Scott, 2011; Wilson Mantilla et al., 2021). Whereas Late Cretaceous eutherians ranged from invertivory, faunivory, and animal- and plant-dominated omnivory, they were less dietarily diverse compared to contemporaneous metatherians and did not expand beyond invertivory until the Campanian (at least in North America; Harper, 2012; Harper et al., 2019), well after metatherians had. Thus, our study does not exclusively support either the Suppression Hypothesis or the Early Rise Hypothesis. The Suppression Hypothesis predicts that the ecomorphological diversity (number of diets) and disparity (magnitude of morphological difference) in metatherians was low and stable throughout the Late Cretaceous. Whereas our quantitative results of dental disparity and ecomorphological diversity are consistent with this hypothesis — that is, dental disparity does not significantly change through the Late Cretaceous and most metatherians were invertivores and soft-invertebrate specialists (Figure 6); we posit that inclusion of, for example, the middle Turonian stagodontids (Fumodelphodon and Hoodootherium) and aquiladelphids (Scalaridelphys) and the Lancian Nanocuris would likely increase dental disparity and diversity of dietary categories recorded for at least those intervals. Moreover, the ecomorphological diversity and disparity values are likely greater than those of other contemporary mammalian clades, which exhibit a smaller range of diets and dental morphologies. The Early Rise Hypothesis predicts that rapid increases in ecomorphological diversity and disparity of metatherians began in the late Late Cretaceous. Although our DFA shows that metatherians were mostly invertivores and soft-invertebrate specialists, it also shows that by the pre-Aquilan — prior to the ecological radiation of angiosperms — they had begun to exploit other diets as well, including plant-dominated omnivory (Figures 6 – 7). Whereas dietary diversity and disparity were both stable throughout the Late Cretaceous, they were elevated relative to contemporary mammalian groups; we hypothesize that the diversification that produced this relatively high dietary diversity and dental disparity arose during the late Early Cretaceous. As such, we would suggest that the ecomorphological expansion of NA metatherians was not temporally correlated with the ecological rise of angiosperms but perhaps with their earlier taxonomic diversification (Cohen et al., 2020), which occurred during the Cretaceous Terrestrial Revolution (ca. 125 – 80 Ma). As new species of angiosperms appeared during their taxonomic diversification, they may have provided new food resources for metatherians to exploit, thus catalyzing the ecomorphological expansion of metatherians. Or perhaps other possible co-occurring factors during the Cretaceous Terrestrial Revolution, such as the extinction of eutriconodontans and spalacotherioids (Grossnickle and Polly, 2013; Cohen et al., 2020), allowed metatherians to expand into newly vacated niches. Future studies should test this hypothesis by applying DTA to samples of Early Cretaceous metatherians; however, to achieve this, additional field work should be undertaken to bolster the sparse fossil record from this interval.	en	Brannick, Alexandria L., Fulghum, Henry Z., Grossnickle, David M., Wilson Mantilla, Gregory P. (2023): Dental ecomorphology and macroevolutionary patterns of North American Late Cretaceous metatherians. Palaeontologia Electronica (a 48) 26 (3): 1-42, DOI: 10.26879/1177, URL: http://dx.doi.org/10.26879/1177
