Brachyura, Linnaeus, 1758

Klompmaker, Adiël A., Starzyk, Natalia, Fraaije, René H. B. & Schweigert, Günter, 2020, Systematics and convergent evolution of multiple reef-associated Jurassic and Cretaceous crabs (Decapoda, Brachyura), Palaeontologia Electronica (a 32) 23 (2), pp. 1-54 : 4-6

Infraorder BRACHYURA Linnaeus, 1758 Section DROMIACEA De Haan, 1833

Superfamily HOMOLODROMIOIDEA Alcock, 1900

Family GONIODROMITIDAE Beurlen, 1932

Genus EODROMITES Patrulius, 1959

Type species. Prosopon grande von Meyer, 1857 , by original designation and monotypy (= Eodromites guenteri Starzyk, 2015b ).

Included species. Eodromites bernchrisdomiorum sp. nov., E. cristinarobinsae sp. nov.; E. depressus (von Meyer, 1857) as Prosopon ; E. dobrogea (Feldmann, Lazăr, Schweitzer, 2006) , as Cycloprosopon ; E. grandis (von Meyer, 1857) , as Prosopon ; E. nitidus (A. Milne Edwards, 1865) , as Ogydromites ; E. polyphemi (Gemmellaro, 1869) , as Prosopon ; E. rostratus (von Meyer, 1840) , as Prosopon ; E. rotundus Starzyk, 2015b .

Remarks. Eodromites guenteri resembles E. grandis in outline and groove pattern. Moreover, the neotype of E. grandis originates from the same upper Kimmeridgian strata and from the same region in Germany. Pits on the epibranchial region and just posterior to the upper orbital margin on the internal mold are key features present in the sole specimen of E. guenteri to distinguish it from E. grandis , which would not have these pits (Starzyk, 2015b). These pits are, however, not consistently present on species represented by many specimens. For example, the posteriormost pits have been observed in only part of the large specimens of E. cristinarobinsae sp. nov. (MAB k2950, MAB k3589) and only on one side of the latter specimen. Only one medium-sized specimen of E. cristinarobinsae sp. nov. exhibits all three pits (MAB k2626) and one medium-sized specimen may have both epibranchial pits (MAB k2637), but is otherwise identical to conspecifics. Based on a limited number of relatively small specimens ascribed to E. bernchrisdomiorum sp. nov. from the Oxfordian of Poland (I-F/MP/3604/1533/08, I-F/MP/6259/1588/ 11, I-F/MP/3233/1532/08, I-F/MP/6258/1588/11, IF/MP/1701/1517/08, I-F/MP/2932/1532/08), a pit posterior to the right upper orbital margin can be found in some specimens (I-F/MP/3233/1532/08, IF/MP/6258/1588/11, I-F/MP/2932/1532/08), but not for another specimen with relatively wellexposed orbital margins (I-F/MP/6259/1588/11); pits were not seen on the epibranchial regions of these specimens. Unfortunately, no sufficiently well-preserved specimens of Late Jurassic E. grandis from Germany were available to assess the degree of variation of pits. To conclude, the variable presence of pits within species of Eodromites demonstrates that the presence/absence of pits is problematic to use to distinguish species. The ratio of length from the outer orbital angle to the cervical groove at the lateral margin divided by the length from the tip of the rostrum to the cervical groove axially would be another difference between E. grandis and E. guenteri (Starzyk, 2015b) . The one specimen of E. guenteri known has a ratio (0.37) comparable to the neotype of E. grandis from the same region and age [0.36, using Wehner (1988, plate 7.1), also shown in Schweitzer and Feldmann (2008a, plate 4F)] or even higher for the new German specimen of E. grandis (0.43, Figure 2A ). Furthermore, the neotype of E. grandis is comparable in size to E. guenteri (10.4 vs 10.6 mm max. width, resp.) and would plot very close to E. guenteri in figure 3 in Starzyk (2015b). According to Starzyk (2015b), E. guenteri has a rostrum that is incised in the middle in contrast to congenerics. However, multiple species of Eodromites exhibit this incision, including E. dobrogea (Schweitzer and Feldmann, 2010b) , specimens of E. grandis including the neotype (Wehner, 1988, plate 7.1; Schweitzer and Feldmann, 2010a; Figure 2A ), and E. cristinarobinsae sp. nov. (Klompmaker et al., 2012; Figures 3 , 4 ). Eodromites guenteri is also said to have the longest augenrest of all studied species (Starzyk, 2015b), but the orbital structure is also long in the new German specimen of E. grandis ( Figure 2F ). As the proposed differences are less prominent to non-existing, we argue that E. guenteri is a junior synonym of E. grandis .

After Starzyk (2015b) described Eodromites hyznyi and E. rotundus , both species were transferred to Tanidromites by Schweitzer et al. (2017) based on narrow, triangular fronts similar to Tanidromites , the straighter lateral margins more comparable to Tanidromites , the relatively shallow augenrest, and the lower orbital rim not extending beyond the upper orbital margin as in Tanidromites . Although the rostrum of E. rotundus appears less downturned and the carapace surface seems more uneven than most species of Eodromites (Starzyk, 2015b, figure 6), a straighter lateral margin does not apply to E. rotundus (narrowing posteriorly instead), the lower orbital rim can extend beyond the upper orbital margin for Eodromites (type species E. grandis , Figure 2A ), and augenrests with comparable depth to E. rotundus are also found in E. bernchrisdomiorum sp. nov. Moreover, the base of the rostrum of E. rotundus is fairly wide as in Eodromites . Thus, placement of E. rotundus in Tanidromites does not appear to be strongly supported, so we transfer this species into its original genus, Eodromites . We agree with Schweitzer et al. (2017) that Eodromites hyznyi fits better in Tanidromites .

Another taxon to reconsider here is Eodromites aequilatus , which Schweigert and Koppka (2011) placed in Eodromites , followed by subsequent authors (Starzyk, 2015b; Hyžný et al., 2015; Schweitzer et al., 2017, 2018), although no detailed explanation was provided. In fact, E. aequilatus was compared to multiple morphologically similar species of Tanidromites , and it was concluded that the similarities between Eodromites and Tanidromites suggest that they are phylogenetically close (Schweigert and Koppka, 2011). Subsequently, Starzyk (2015b, p. 17) mentioned that E. aequilatus is close to Tanidromites in carapace shape and details of the augenrest, although “the augenrest in Tanidromites is flat, whilst in Eodromites it is deep (concave).” However, T. alexandrae and T. schweitzerae do bear deeper augenrests. Furthermore, E. aequilatus fits the diagnosis of Tanidromites (Starzyk, 2016) , including the tall flanks and the similarity in overall rectangular shape, unlike species of Eodromites that tend to narrow much more posteriorly. An inflated subhepatic region as in E. aequilatus can also be seen in Tanidromites insignis (Schweigert and Koppka, 2011, figure 6C) and Tanidromites scheffnerae (I-F/MP/6261/1588/11, I-F/MP/6263/1588/ 11), and a circle of hepatic pits (=antennar extensor muscle scars), initially suggested to be characteristic of Eodromites including E. aequilatus (Starzyk, 2015b) , is also present in Tanidromites scheffnerae from Poland and Austria (pers. obs. AAK) and T. nightwishorum sp. nov. from Austria (see below). Pithonoton , in which E. aequilatus was placed prior to Schweigert and Koppka (2011) placing this species in Eodromites , is mentioned to have short lateral sides and no subhepatic swelling for the specimens examined (Schweitzer and Feldmann, 2008a), unlike E. aequilatus . In conclusion, we transfer E. aequilatus to Tanidromites .

Figures

FIGURE 2. Specimens of the crab Eodromites spp. from the Late Jurassic of Europe. A, F, G, Eodromites grandis (von Meyer, 1857) from the Upper Jurassic (upper Kimmeridgian) coral limestones of Saal an der Donau in southern Germany in dorsal, frontal, and left-lateral views, resp. (SNSB-BSPG 2016 XXI 404). B-E, Holotype of Eodromites bernchrisdomiorum sp. nov. from the Upper Jurassic (lower-middle Oxfordian) deposits of Ogrodzieniec in southern Poland in dorsal, frontal, right-lateral, and orbital views, resp. (I-F/MP/6259/1588/11). E, an oblique view of right orbital structure, primarily the lateral margin with a wide fissure. H-K, Late Jurassic (Oxfordian) Eodromites bernchrisdomiorum sp. nov. from southern Poland in dorsal view (H, I-F/MP/4874/1534/08, Niegowonice, middle-late Oxfordian; I, I-F/ MP/6255/1588/11, paratype, Niegowonice, middle-late Oxfordian; J, I-F/MP/6258/1588/11, Ogrodzieniec, early-middle Oxfordian, paratype; K, I-F/MP/1369/1508/08, Bzów, middle Oxfordian). L-O, Holotype of Eodromites polyphemi (Gemmellaro, 1869) from the Late Jurassic (Tithonian) of Sicily, Italy, in dorsal, frontal, right-lateral, and left-lateral views, resp. (MGUP-020.18). Scale bar width is 5.0 mm, except for E (1.0 mm).

FIGURE 3. Length-width ratios versus maximum width of carapaces of Eodromites grandis compared to E. cristinarobinsae sp. nov. (previously identified as E. grandis). Data: Appendix 2.

FIGURE 4. Specimens of the crab Eodromites cristinarobinsae sp. nov. from the mid-Cretaceous (lower upper Albian) reef limestones of Koskobilo, northern Spain. A-C, dorsal views (holotype MGSB78750, paratype UF 271883, and paratype MAB k3592, resp.). D-F, frontal views (MGSB78750, UF 271883, and MAB k2638, resp.). G, H, right- and left-lateral views (MAB k2950 and MAB k2953, resp.). I, oblique view of lateral part of orbital structure with fissure (MAB k2626); upper orbital margin incomplete; height figure ~1.0 mm. A, D, G, and H colored dark and subsequently coated with ammonium chloride prior to photography; from Klompmaker et al. (2012, figure 5B, H, J, and K, reproduced with permission). Those images are not published under the terms of the CC-BY license of this article. For permission to reuse, please see Klompmaker et al. (2012). Scale bar width equals 1.0 mm.