Costacopluma nicksabani, Klompmaker & Martin & Hyžný & Bowman & Phillips & Portell, 2025
publication ID |
https://doi.org/10.5252/geodiversitas2024v47a13 |
publication LSID |
urn:lsid:zoobank.org:pub:F5144147-C045-48FD-8128-7F822CDE6B18 |
DOI |
https://doi.org/10.5281/zenodo.17243654 |
persistent identifier |
https://treatment.plazi.org/id/F77987B8-FFAA-FF8D-11C7-CFF7AEE3F994 |
treatment provided by |
Plazi |
scientific name |
Costacopluma nicksabani |
status |
sp. nov. |
Costacopluma nicksabani n. sp.
( Figs 17 View FIG ; 18 View FIG ; Table 1 View TABLE ; Appendices 1A-E; 3)
urn:lsid:zoobank.org:act:
Costacopluma grayi View in CoL – Feldmann et al. 2014: 137, pls 1-2.— Martínez-Díaz et al. 2016: figs 5.1-5.8, 6.4.
TYPE MATERIAL. — Holotype. United States • 1specimen; Alabama, Lowndes County, Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), ALMNH loc. 3; Clayton Formation, Pine Barren Member , lower middle NP2 nannofossil zone; Paleocene (lower Danian); ALMN-H: Paleo:21453 (carapace). GoogleMaps
Paratypes. United States • 1 specimen; same as for the holotype; ALMNH: Paleo:13539 (carapace) GoogleMaps • 1specimen; idem; ALMNH: Paleo:21454 (carapace) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21455 (carapace) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21456 (carapace) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21457 (carapace) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21458 (carapace) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21459 (carapace) GoogleMaps • 1 specimen; idem; MMNS IP-7940.1 (carapace) GoogleMaps • 1 specimen; idem; UF 247378 (pair of propodi and dactyli) GoogleMaps .
ETYMOLOGY. — In honor of the legendary American college football coach Nick Saban, who led the University of Alabama team from 2007-2023, winning six national and nine SEC championships with the Crimson Tide. Also, Nick’s Kids Foundation has made a tremendous societal impact in Alabama and beyond.
ADDITIONAL MATERIAL EXAMINED. — United States • 13specimens; Alabama, Lowndes County, Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), ALMNH loc. 3; Clayton Formation, Pine Barren Member , lower middle NP2 nannofossil zone; Paleocene (lower Danian); ALMNH: Paleo:5918 (carapaces/venters) GoogleMaps • 51 specimens; idem; ALMNH: Paleo:21497 (51 carapaces/venters) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21498 (propodus) GoogleMaps • 1 specimen; idem; ALMNH:Paleo:21499 (carapace with meri and partial carpi) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21500 (merus) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21501 (carapace) GoogleMaps • 1specimen; idem; ALMN-H: Paleo:21502 (venter) GoogleMaps • 1 specimen; idem; ALMNH: Paleo:21503 (merus) GoogleMaps • 26 specimens; idem; ALMNH: Paleo:21504 (carapaces/ venters) GoogleMaps • 1 specimen; idem; MMNS IP-6478 (carapace) GoogleMaps • 1 specimen; idem; MMNS IP-6479 (carapace) GoogleMaps • 1specimen; idem; MMNS IP-6480 (venter) GoogleMaps • 1 specimen; idem; MMNS IP-6481 (carapace) GoogleMaps • 13 specimens; idem; MMNS IP-7257 (carapaces, incl. carapace with base cheliped incl. merus) GoogleMaps • 1 specimen; idem; MMNS IP-7268 (carapace) GoogleMaps • 3 specimens; idem; MMNS IP-7296 (2 carapaces, 1 propodus) GoogleMaps • 6 specimens; idem; MMNS IP-7940.2-7 (carapaces) GoogleMaps • 1 specimen; idem; UF 235556 (carapace) GoogleMaps • 1 specimen; idem; UF 235557 (carapace) GoogleMaps • 1 specimen; idem; UF 235558 (carapace) GoogleMaps • 1 specimen; idem; UF 235559 (carapace) GoogleMaps • 1 specimen; idem; UF 235560 (carapace) GoogleMaps • 1 specimen; idem; UF 235562 (carapace) GoogleMaps • 1 specimen; idem; UF 235563 (carapace) GoogleMaps • 1 specimen; idem; UF 235564 (carapace) GoogleMaps • 1 specimen; idem; UF 235565 (carapace) GoogleMaps • 1 specimen; idem; UF 235566 (carapace) GoogleMaps • 1 specimen; idem; UF 235567 (carapace) GoogleMaps • 1 specimen; idem; UF 235568 (carapace) GoogleMaps • 11 specimens; idem; UF 235569 (10 carapaces and 1 venter) GoogleMaps • 1 specimen; idem; UF 235570 (fixed finger) GoogleMaps • 1 specimen; idem; UF 235571 (propodus) GoogleMaps • 1 specimen; idem; UF 235577 (carapace with propodus) GoogleMaps • 1 specimen; idem; UF 247377 (cheliped propodus) GoogleMaps • 1specimen; idem; UF 254039 (carapace) GoogleMaps • 1 specimen; idem; UF 303795 (carapace) GoogleMaps • 1 specimen; idem; UF 303796 (carapace) GoogleMaps • 1 specimen; idem; UF 303797 (carapace) GoogleMaps • 1 specimen; idem; UF 303798 (carapace) GoogleMaps • 1 specimen; idem; UF 303799 (carapace) GoogleMaps • 1 specimen; idem; UF 303800 (carapace) GoogleMaps • 1 specimen; idem; UF 303802 (carapace) GoogleMaps • 1 specimen; idem; UF 303803 (carapace) GoogleMaps • 1 specimen; idem; UF 303804 (carapace) GoogleMaps • 1 specimen; idem; UF 303805 (carapace) GoogleMaps • 1 specimen; idem; UF 303806 (venter) GoogleMaps • 1 specimen; idem; UF 303807 (carapace) GoogleMaps • 1 specimen; idem; UF 303808 (carapace) GoogleMaps • 1 specimen; idem; UF 303809 (carapace) GoogleMaps • 1 specimen; idem; UF 303810 (carapace) GoogleMaps • 1 specimen; idem; UF 303811 (carapace) GoogleMaps • 1 specimen; idem; UF 303813 (carapace) GoogleMaps • 1 specimen; idem; UF 303814 (carapace) GoogleMaps • 1 specimen; idem; UF 303816 (carapace) GoogleMaps • 1 specimen; idem; UF 303817 (carapace) GoogleMaps • 1 specimen; idem; UF 303818 (carapace) GoogleMaps • 1 specimen; idem; UF 303820 (propodus) GoogleMaps • 1specimen; idem; UF 303821 (cheliped) GoogleMaps .
TYPE HORIZON. — Pine Barren Member of the Clayton Formation, lower middle NP2 nannofossil zone, lower Danian.
TYPE LOCALITY. — ALMNH loc.3: Mussel Creek roadcut ( 31°58’17”N, 86°42’15”W), Lowndes County, Alabama, United States.
DIAGNOSIS. — Carapace relatively small (usually < 15 mm maximum width), subrectangular, wider than long (l/w ratio c. 0.89), widest point posterior to mid-length. Fronto-orbital margin c. 70% of maximum width; lateral margins somewhat diverging posteriorly, fairly straight, but more convex anteriorly; posterior margin straight. Rostrum bilobed, inclined downward, slightly longer than wide, minimum width in dorsal view c. 8% of maximum carapace width. Outer orbital spine small, triangular, directed forward, about as short as spine on lower orbital margin. Dorsal carapace containing three tubercular transverse ridges of intermediate width on average, with rounded tops; anterior ridge sinuous, uninterrupted, diminishes toward but reaches lateral margins. Cardiac region raised, tubercular, with convex and flattened ridge anteriorly and raised extension axially directed posteriorly. Gentle swellings with tubercles just anterior to innermost part of posterolateral margins. Pleon of male narrow, widening somewhat to posterior; with transverse ridges on somites 3-6; telson and sternite 6 unfused; somites 3-5 fused but with sutures visible. Pleon of female with transverse ridges on somites 2-5; all somites and telson unfused; somites 1-5 much wider than long; somite 6 wider than long; telson triangular with rounded tip.
MEASUREMENTS. — See Table 1. View TABLE
DESCRIPTION
Carapace relatively small (usually < 15 mm maximum width), subrectangular, wider than long (l/w ratio c. 0.89), widest point posterior to mid-length, weakly vaulted transversely, moderately vaulted longitudinally. Margins rimmed with granules. Fronto-orbital margin c. 70% of maximum width, sinuous; lateral margins somewhat diverging posteriorly, fairly straight, but more convex anteriorly; posterolateral margin slightly concave; posterior margin straight. Rostrum bilobed, inclined downward, slightly longer than wide, minimum width in dorsal view c. 8% of maximum carapace width, narrowest point about halfway rostrum, with two lobes distally carrying tubercles, tip concave in dorsal view, lateral margins rimmed and with row of granules. Orbital margin rimmed with tubercles; upper orbital margin somewhat thicker than lateral and lower orbital margins; lower orbital margin with forwardly-directed spine; outer orbital spine small, triangular, directed forward, about as short as spine on lower orbital margin. Orbital cavity subovate but with angle at outer orbital spine, faint ridge of granules dividing outer and inner parts. Eyestalks elongated. Epigastric regions consisting of small, gentle swellings. Dorsal carapace containing three tubercular transverse ridges of intermediate width on average, with rounded tops; anterior ridge sinuous, uninterrupted, diminishes toward but reaches lateral margins; median ridges directed anterolaterally, straight, not connecting axially, reaching lateral margins; posterior ridges directed posterolaterally, not connecting axially, reaching posterolateral margins, curving more laterally in outermost part. Posterior part of mesogastric region raised, tubercular, connecting with anterior ridge where it narrows, with two posterior gastric pits near base. Cardiac region raised, tubercular, with convex and flattened ridge anteriorly and raised extension axially directed posteriorly. Gentle swellings with tubercles just anterior to innermost part of posterolateral margins. Other carapace regions not discernible. Dorsal carapace grooves absent except for short groove lateral to posterior part of mesogastric region ending in ovals pits anteriorly. Cuticular surface of dorsal carapace regions between ridges, in front of anterior ridge, and posterior to cardiac region pitted. Flanks straight; about a quarter in height of maximum carapace width; with groove starting at lateral margin, resulting sometimes in a weak notch, near position where anterior ridge connects to lateral margin; groove curving forward and becoming deeper near base of flank; flank tubercular in posterior part, mostly smooth in anterior third but with some tubercles in anteriormost part. Pterygostome subtriangular and with posterior extension, with rim posteriorly and inward margin, mostly smooth. Buccal area with pit axially. Maxillipeds not preserved. Sternum suboval, widest at 5 th sternite. Sternites 1 and 2 fused, separated by groove, triangular jointly; sternite 1 triangular with sharp tip, with tubercles; sternite 2 much wider than long, with short axial groove, with tubercles, widening toward sternite 3. Sternite 3 fused to sternite 4 but marked by transverse groove, with two lobes on posterior margin on either side of tip of sternopleonal cavity for males but with deep depression axially for females, straight anteriorly, tubercular. Sternite 4 trapezoidal, tubercular, not flattened but concave, widening more laterally; with small anterolaterally oriented projection in anterolateral corner, about straight on anterior side for females and males, not extending much if anything beyond sternite 3. Sternites 5-7 with transverse, tubercular ridge widening inward. Sternites 4-6 with long episternal projections pointing posteriorly, episternal projection not preserved for sternite 7. Sternite 8 poorly preserved. Sternopleonal cavity of male deep, narrow, smooth, with sutures of 4/5, 5/6, and 6/7 extending to base of cavity but not connecting, suture 7/8 partially preserved, axial slit at level of sternite 7; sternopleonal cavity extends to upper part of sternite 4 and marked by clear rim at tip, small press button on sternite 5 on upper part of slope near sternite 4. Sternopleonal cavity of female incompletely preserved, but broader than male; without press button, deep, smooth, with sutures of 4/5, 5/6, and 6/7 extending to base of sternopleonal cavity but not connecting, with flat bottom between sternites 4-6, sternopleonal cavity extends to upper part of sternite 3 and without rim at tip; position of tip of telson marked by granules without forming rim, near base of sternite 3; subcircular oviduct on anterior part of sternite 6 near sternite 5, adjacent to base of sternopleonal cavity. Pleon of male narrow, widening somewhat to posterior; with transverse ridges on somites 3-6, ridge of somite 6 with tubercles, ridges of somites 3-5 pitted; pitted telson triangular with rounded tip; telson and sternite 6 unfused; somites 3-5 fused but with sutures visible; somites 1-2 much shorter than other somites, without ridge in center, with rim on anterior margin for somite 1, with bump in center of somite 2. Pleon of female with pitted transverse ridges on somites 2-5; all somites and telson unfused; somites 1-5 much wider than long; somite 6 wider than long, with tubercles on transverse ridge; telson triangular with rounded tip, pitted. Male pleopod 1 (gonopod 1) curved, open at tip, at position of somite 6.
Chelipeds isochelous or slightly heterochelous. Cheliped propodus without fixed finger wider than tall, upper margin with tubercular rim, lower margin rounded, subtrapezoidal in outer view; outer side convex, with shallow and longitudinal depression near upper margin, mostly pitted cuticular surface but with bands of tubercles near lower and upper margins; inner side flattened to slightly convex, with band of tubercles on lower third; fixed finger taller than wide in cross-section, flat bottom, occlusal surface with poorly preserved teeth decreasing in size to distal part, outer and inner sides with two ridges covered with granules near lower margin separated by groove, setal pits present on outer and inner sides, probably about as long as upper margin. Cheliped dactylus poorly preserved but with two ridges on upper margin of outer side, with setal pits on outer side. Cheliped carpus not preserved. Cheliped merus longer than tall, spines forming ridge on lower margin, scattered granules on convex outer surface, dense granules on upper margin, lower surface flat and mostly smooth. Cheliped ischium triangular, small, surface covered with tubercles, with two spines near articulation with merus. Non-cheliped appendages such as merus appear long; rest of these appendages not preserved.
REMARKS
Specimens from the early Danian of Mussel Creek were previously ascribed to C. grayi ( Feldmann et al. 2014; Martínez-Díaz et al. 2016). A restudy of the type and new specimens of C. grayi from the Eocene of Alabama and additional specimens from Mussel Creek render this hypothesis untenable. Differences include a proportionally narrower rostrum for C. grayi ( Figs 12A, F View FIG ; 13B View FIG ; 15F, G View FIG ; Table 1 View TABLE ), a narrower median ridge with fewer tubercles ( Figs 14 View FIG ; 17 View FIG ), an apparently less tubercular propodus compared to C. nicksabani n. sp. ( Figs 14D View FIG ; 18J View FIG ), and a less tubercular sternite 4.
Costacopluma nicksabani n. sp. differs from all other congenerics as well, compared alphabetically below, using the papers in which those species were first described and other papers as needed. Costacopluma australis View in CoL has an overall similar outline, but the rostrum is protruding less prominently relative to the outer orbital spine than in the new species and the anteriormost transverse ridge appears to be concave forward (Feldmann et al. 1995: fig. 16) rather than sinuous. Costacopluma bifida View in CoL has an anterior ridge said to be ‘interrupted’ medially ( Collins et al. 1994: 30), which is not the case in C. nicksabani n. sp. Moreover, this ridge is mentioned to not reach the lateral margin, but it does in the new species. Costacopluma bishopi View in CoL has much broader transverse ridges ( Vega & Feldmann 1992: fig. 4). Costacopluma binodosa View in CoL does not have the front preserved, limiting the number of characters to compare to, but this species has somewhat more prominent nodes just anterior to the posterolateral margins ( Collins & Wienberg Rasmussen 1992: fig. 23). Moreover, this species has a posterior portion of the cardiac region that is less raised based on a cast and photos of the type specimen made by AAK. Costacopluma maroccana View in CoL has a more ovate outline resulting from more rounded lateral margins ( Ossó-Morales et al. 2010: fig. 7; ALMNH:Paleo:20599). Costacopluma mexicana View in CoL has much broader transverse ridges ( holotype in Luque et al. 2017: fig. 13F). Costacopluma mamethioupamei View in CoL exhibits narrower transverse ridges (Hyžný et al. 2016: fig. 5). Costacopluma nordestina View in CoL exhibits a more rounded posterior margin, the lateral margins are more rounded, and the median ridge displays more tubercles ( Feldmann & Martins-Neto 1995: fig. 1; Luque et al. 2017: fig. 5G, H). Costacopluma salamanca View in CoL is close in terms of ridges and their tubercles, but it is rounder anteriorly so that the fronto-orbital margin takes up a lower proportion of the maximum width ( c. 63% vs c. 70% for C. nicksabani n. sp.), and the rostrum appears smaller (see Feldmann et al. 1997: fig. 3.2). Costacopluma senegalensis View in CoL has much more rounded lateral margins ( Gorodiski & Rémy 1959: pl. 19.1). Costacopluma squiresi View in CoL exhibits a much more pronounced depression between the mesogastric and cardiac regions and the tubercles on the transverse ridges are smaller than in C. nicksabani n. sp. ( Nyborg et al. 2009: fig. 2). Costacopluma texana View in CoL is morphologically, geographically ( Texas, United States), and stratigraphically (late Danian instead of early Danian) close to C. nicksabani n. sp., so a more detailed comparison is warranted. The median ridge is wider and flatter in C. texana View in CoL , and the anterior and posterior ridges are flatter topped too. Moreover, C. texana View in CoL has a significantly higher length-width ratio (Mann-Whitney p = 0.0005; Figs 15-18 View FIG View FIG View FIG View FIG ; Table 1 View TABLE ), appears to exhibit a thicker upper orbital rim ( Fig. 15G, I View FIG vs Fig. 16D, G View FIG ; 17B View FIG ), has an oval-shaped oviduct rather than subcircular in C. nicksabani n. sp. ( Fig. 16K View FIG vs Fig. 17M View FIG ), the transverse ridges on sternites 5-6 are taller in at least females, the outer lateral margins of sternite 4 appear more flared up on average, and the press button on males is larger ( Fig. 16L View FIG vs Fig. 18N View FIG ).
We did not observe obvious ontogenetic variation, perhaps because of the limited size range of specimens. Sexual dimorphism is not observed on the dorsal carapace, but it is evident on the ventral side (wider female pleon and other characters, see description). Intraspecific variation is limited despite the high number of specimens.
For lesser preserved specimens with cuticle, the tubercles on the transverse ridges are less obvious. Carapace ornamentation is difficult to discern on internal molds (ALMN-H:Paleo:21497A, 1 specimen of UF 235569). The sediment surrounding Mussel Creek specimens varies from tan to dark gray and from friable to fully lithified. This observation may indicate differing taphonomic conditions.
The gonopods preserved in three specimens of Costacopluma nicksabani n. sp. (ALMNH:Paleo:21457, MMNS IP-7940.1, UF 303806; Fig. 16I, M View FIG ) resemble those in extant retroplumids ( de Saint Laurent 1989). The preservation of gonopods in fossil brachyurans is uncommon (e.g., Karasawa & Schweitzer 2006: 42; Garassino et al. 2013: 356), and they had not been recognized within Costacopluma and fossil Retroplumidae until this paper. These small pleonal appendages, often taxonomically important for extant crabs, are less calcified than walking appendages and claws and tend to be covered by the pleon within the sternopleonal cavity. Fossil brachyuran species with these structures have been more frequently recognized over the last decade, mostly in specimens that have the pleonal somites incompletely preserved exposing structures underneath ( Smirnov 1929; Secrétan 1975; Karasawa & Kato 2001, 2019; Guinot & Breton 2006; Karasawa & Schweitzer 2006; Artal et al. 2008; Feldmann et al. 2011; Schweitzer & Feldmann 2015; Luque et al. 2018, 2019; Pereyra et al. 2019; Lima et al. 2020; Pereyra & Verde 2020; Hyžný et al. 2022; Kovalchuk et al. 2023). The preservation of delicate tips of gonopods herein is even rarer.
ALMNH |
Alabama Museum of Natural History |
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.
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InfraOrder |
Brachyura |
SuperFamily |
Retroplumoidea |
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Genus |
Costacopluma nicksabani
Klompmaker, Adiël A., Martin, P. George, Hyžný, Matúš, Bowman, Andrew R., Phillips, George E. & Portell, Roger W. 2025 |
Costacopluma grayi
FELDMANN R. M. & SCHWEITZER C. E. & PORTELL R. W. 2014: 137 |