Palaeastacus fuciformis ( Schlotheim, 1822 )

Devillez, Julien & Charbonnier, Sylvain, 2021, Review of the Late Jurassic erymoid lobsters (Crustacea: Decapoda), Geodiversitas 43 (2), pp. 25-73 : 50-52

Palaeastacus fuciformis ( Schlotheim, 1822)

( Fig. 12 )

Macrourites fuciformis Schlotheim, 1822: 30 , pl. 2, fig. 2.

Glyphea fuciformis – Münster 1839: 16, pl. 8, figs 1-2.

Glyphea intermedia – Münster 1839: 17, pl. 8, fig. 6-7.

Glyphea crassula – Münster 1839: 17, pl. 8, fig. 4 (non 5).

Glyphea elongata – Münster 1839: 18, pl. 8, fig. 11-12 (non figs 8-10).

Eryma fuciformis – Bronn 1849: 579. — Oppel 1861: 359. — Oppel 1862: 41, pl. 9, figs 2-6. — Beurlen 1928: 164. — Glaessner 1929: 154. — Vialle 1948: 61. — Kuhn 1961: 22. — Secrétan 1964: 68.

Astacus fuciformis – Quenstedt 1852: 268, pl. 20, fig. 14. — Quenstedt 1867: 320, pl. 25, fig. 14. — Quenstedt 1885: 409, pl. 32, fig. 7.

Eryma elongata – Oppel 1861: 358. — Oppel 1862: 37, pl. 8, figs 1-2.

Enoploclytia fuciformis – Van Straelen 1925: 285.

Clytia elongata – Beurlen 1928: 170.

Palaeastacus fuciformis – Förster 1966: 130, fig. 25. — Förster & Rieber 1982: 774, 777. — Frickhinger 1994:122, figs 218-219. — Schweigert et al. 2000: 5. — Schweitzer & Feldmann 2001: 174. — Schweigert & Röper 2001: 8, fig. 5. — Garassino & Schweigert 2006: 9, fig. 8, pl. 1, fig. 3, pl. 11, fig. 5. — Schweitzer et al. 2010: 25. — Charbonnier & Garassino 2012: 859, 864, fig. 3d. — Karasawa et al. 2013: 102, table 1. — Audo et al. 2014: 463. — Odin et al. 2019: 654, fig. 7A-C, ap. 1.

TYPE MATERIAL. — Holotype MFN 2236 P1383/8 MB.A.0251 . TYPE LOCALITY. — Solnhofen area, Bavaria, Germany. TYPE AGE. — Tithonian .

DESCRIPTION

Carapace

Sub-cylindrical carapace; short, spiny rostrum; fusiform intercalated plate; orbital notch widely curved; narrow post-orbital area; elongated cephalic region; wide deep cervical groove, slightly sinuous, joined to dorsal margin and to antennal groove; deep antennal groove; short, shallow gastro-orbital groove, joined to cervical groove at carapace mid-height; postcervical and branchiocardiac grooves subparallel, then converging under the level of the gastro-orbital groove and diverging before their junc-tion with hepatic groove, slightly inclined, not joined to dorsal margin; wide, deep postcervical groove, joined to hepatic groove; shallow branchiocardiac groove, joined to the posterior extremity of hepatic groove; hepatic groove concavo-convex, joined to cervical groove; deep inferior groove, joined to hepatic groove.

Pleon and uropods

Somites with wide subtriangular pleurites, with a bulge on their basis; telson with two longitudinal crests along the lateral margin; uropods as long as telson; uropodal endopods with a longitudinal carina; uropodal exopods with a diaeresis, and with a longitudinal carina.

Cephalic appendages

Last segment of antennular peduncles (basipodite) articulated with two flagella, flagella made of numerous and short cylindrical articles; antennas made of numerous and short cylindrical articles; short, triangular scaphocerite.

Thoracic appendages

Elongated Mxp3, with small spines on the ventral margin of each article excepted the two distal ones; chelate P1; P1 propodus short, subrectangular; wide P1 fingers, as long as propodus, straight dorsally, slightly curved downward, equal in length, with a distal hook; occlusal margin with very small teeth, closely spaced; P1 carpus short, subtriangular; elongated P1 merus; P2-P3 chelate.

Ornamentation

Carapace with a heterogeneous ornamentation; branchial, hepatic and pterygostomial regions densely covered by small tubercles, cardiac region covered by small tubercles and some spiny tubercles directed forward, cephalic region with strong and widely spaced spines directed forward and small tubercles; intercalated plate covered by a row of tubercles; presence of an antennal spine; tergites and pleurites of pleonal somites covered by small depressions; telson with two small spines on external margin; uropodal endopods with two small spines on external margin; uropodal exopods with a spine on external margin anterior to the diaeresis; P1 propodus covered by longitudinal rows of strong spines directed forward; inner margin with a row of strong spines directed forward; P1 carpus covered by rows of strong spines directed forward; P1 merus covered by small tubercles and strong spines directed forward along dorsal and ventral margins; P2-P3 and P5 with small and widely spaced depressions; P4 propodus with posterior spines.

DISCUSSION

Palaeastacus fuciformis is known by many subcomplete specimens. Its assignation to Palaeastacus is based on its typical carapace groove pattern and shape of P1 chelae: short gastro-orbital groove, both postcervical and branchiocardiac grooves joined to the sinuous hepatic groove, short and subrectangular P1 propodus, wide, short and straight fingers.

Except Palaeastacus argoviensis Förster & Rieber, 1982 from the Aalenian, Palaeastacus fuciformis is the only species of the genus to have a sinuous cervical groove. The trajectories of the postcervical and branchiocardiac grooves are also particular: they are convergent under the level of the gastro-orbital groove and become divergent above their junctions to the hepatic groove. Similar trajectories of these grooves are only found in Palaeastacus terraereginae from the Barremian. Another characteristic is the presence of strong spines in the cephalic region while the remaining parts of its carapace are covered by small tubercles. None of other representatives of Palaeastacus exhibits such ornamentation. That of Palaeastacus sussexiensis ( Mantell, 1824) from the Cretaceous is very close but P. fuciformis does not have oblique rows of strong spines in its cardiac region ( Devillez et al. 2016, 2017). The P1 propodus of P. fuciformis is ornamented by longitudinal rows of spines contrary to most of the other species for which the P1 chelae are known.

Figures

FIG. 12. —Palaeastacus rothgaengerae Schweigert & Röper,2001 and Palaeastacus fuciformis (Schlotheim, 1822) from Germany:A, B, holotype BSPG 1993 XXVIII 200 of P. rothgaengerae from the Kimmeridgian of Brunn quarry: general view (A), schema (B); C, D, holotype MFN 2236 P1383/8 MB.A.0251 of P. fuciformis from the Tithonian of Solnhofen:general view (C), schema of the carapace (D); E, specimen MFN 2236 P1383/7 MB.A.2985 from the Tithonian of Eichstätt;F-G, specimen MFN 2236 P1383/7 MB.A.2992 from the Tithonian of Solnhofen:general view (F), schema (G). Abbreviations:a, branchiocardiac groove;a1, antennulae;a2, antenna; b, antennal groove; b1, hepatic groove; c, postcervical groove; d, gastro-orbital groove; di, diaeresis;e, eye; e1e, cervical groove; i, inferior groove; ip, intercalated plate; Mxp3, third maxilliped; pl, pleopod; PoA, postorbital area. Photographs: C, E, F, J. Devillez; A, G. Schweigert. Line drawings: J. Devillez. Scale bars: 1 cm.