Protuberosa protuberosa (Wehner, 1988)

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 : 27

Protuberosa protuberosa (Wehner, 1988)

Figure 15

1988 Prosopon protuberosum Wehner , p. 20, fig. 7, pl. 1.3-1.4.

2000 Prosopon protuberosum Wehner ; Müller et al., fig. 17B.

2009d Protuberosa protuberosa Wehner ; Schweitzer and Feldmann, p. 77, fig. 2.9.

Diagnosis. Carapace widening posteriorly, longer than wide (l/w ratio ~1.2). Very bulbous appearance anterior to branchiocardiac groove, in particular mesobranchial, epibranchial, base mesogastric,

protogastric, and hepatic regions. Ridge with two tubercles on flank. Tubercles scattered across carapace, often with pit in center.

Material studied. Holotype: SNSB-BSPG 2016 XXI 482 ; paratype: SNSB-BSPG 2016 XXI 484 .

Occurrence. Coralgal “Kelheimer Schuttkalk” of Saal an der Donau near Kelheim, southern Germany (Google Earth coordinates: 48.88, 11.94), Late Jurassic (late Kimmeridgian), see Wehner (1988).

Dimensions. ( In mm) Holotype SNSB-BSPG 2016 XXI 482 : max. length excl. rostrum but incl. epigastric swellings (L)=~8.3, max. width (W)=~6.7; paratype SNSB-BSPG 2016 XXI 484 : L=-, W=6.0.

Description. Referral is made to Wehner (1988, p. 20-21) and the English translation in Schweitzer and Feldmann (2009d, p. 77).

Remarks. These two type specimens were housed in the private Sylla collection, but were recently purchased by the Bayerische Staatssammlung für Paläontologie und Geologie, Munich, Germany. Now the specimens have become available for research, a restudy is warranted. We refigure the specimens including the lateral side of the paratype for the first time, showing a peculiar ridge with tubercles ( Figure 15D ) that was only drawn previously (Wehner, 1988, figure 7B).

Recently, Guinot (2019) suggested removing Protuberosa from Prosopidae and hypothesized relatedness to Bucculentidae. Given the strong similarity of Protuberosa to prosopids, Guinot (2019) implied substantial convergent evolution of the carapace of Protuberosa towards prosopids if Protuberosa indeed would be a bucculentid. However, Bucculentum is widest at the hepatic region, has a spiny to three-pronged rostrum, and does not possess a concavity on the lateral side anterior of the cervical groove as seen in other prosopids (e.g., Starzyk et al., 2011; Schweitzer and Feldmann, 2009d; Schweitzer et al., 2018). As Protuberosa does not appear to differ much from other prosopids (see also Figures 11-14), we maintain Protuberosa within Prosopidae.

Figures

FIGURE 11. Specimens of the crab Europrosopon aculeatum (von Meyer, 1857) comb. nov. from the Late Jurassic (Tithonian) of Central Europe, all dorsal views. A, C, F, Specimens from Ernstbrunn, Austria (NHMW 1990/0041/3756, 2007z0149/0005, and 1990/0041/2520, resp., previously identified as Prosopon verrucosum by Schweitzer and Feldmann (2009d). B, Specimen (UF 288714) from the Kotouc quarry (locality 3 of level 6), Czech Republic. D, E, Specimens (LPBIII art 279 and LPBIII art 278, resp.) from Waypoint 162, Romania, previously identified as Prosopon barbulescuae (modified from Schweitzer et al., 2018, figure 13, 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 Schweitzer et al. (2018). Note that the specimen in D is oriented toward the anterior portion of the carapace. Scale bar width equals 2.0 mm.

FIGURE 12. Comparison of length-width ratios relative to specimen size for carapaces of three previously recognized brachyuran species that are synonymized herein: Europrosopon aculeatum (=E. verrucosum and E. barbulescuae). Specimens grew proportionally wider (allometric growth). Data: Appendix 4.

FIGURE 13. Specimen of the crab Laeviprosopon punctatum (von Meyer, 1857) (NHMW 2017/0089/0033) from the Late Jurassic (Tithonian) of Ernstbrunn, eastern Austria. A, dorsal view of carapace. B, right-lateral view. C, frontal view. Scale bar width equals 2.0 mm.

FIGURE 14. Specimen of the crab Prosopon josephcollinsi sp. nov. (NHMW 1990/0041/0738) from the Late Jurassic (Tithonian) of Ernstbrunn, eastern Austria. A, dorsal view of carapace. B, left-lateral view. C, frontal view. D, right-lateral view, angled. Scale bar width equals 5.0 mm.

FIGURE 15. Holo- and paratype of the crab Protuberosa protuberosa (Wehner, 1988) from the Late Jurassic (late Kimmeridgian) of Saal near Kelheim, southern Germany. A, B, dorsal views of carapace of holotype (SNSB-BSPG 2016 XXI 482) (external mold and cast, resp.). C, dorsal view of partial carapace of paratype (SNSB-BSPG 2016 XXI 484). D, right-lateral view of paratype. Scale bar width equals 5.0 mm.