Laeviprosopon fraasi (Moericke, 1889)

Starzyk, Natalia, Van Bakel, Barry W. M., Klompmaker, Adiël A., Schweigert, Günter & Fraaije, René H. B., 2023, A new approach to the systematics of Laeviprosopon (Brachyura: Homolidae), with remarks on the molting process of early brachyurans, Palaeontologia Electronica (a 10) 26 (1), pp. 1-24 : 9-10

Laeviprosopon fraasi (Moericke, 1889)

Figures 1 , 6

1889 Prosopon fraasi Moericke , p. 63, pl. 6, figure 17.

1897 Prosopon fraasi Moericke , p. 63, pl. 6, figure 17.

1895 Prosopon fraasi Moericke. – Remeš, p.

203, pl. 3, figure 15.

1905 Prosopon fraasi Moericke. – Remeš, p. 35.

1925 Avihomola fraasi (Moericke) . – Van Straelen, p. 347.

1929 Nodoprosopon fraasi (Moericke) . – Glaessner, p. 271.

1933 Laeviprosopon fraasi (Moericke) . – Glaessner, p. 180.

1966 Laeviprosopon fraasi (Moericke) . – Patrulius, p. 507.

1988 Laeviprosopon fraasi (Moericke) . – Wehner, p. 119, text-figure 32, pl. 8, figure 4a, 4b.

2008 Laeviprosopon fraasi (Moericke) . – Schweitzer and Feldmann, p. 281, pl. 1.6.

2008 Laeviprosopon sublaeve (von Meyer) . – Schweitzer and Feldmann, p. 278–280, pl. 1.10, 1.11.

Diagnosis. (After Schweitzer and Feldmann,

2008, emended.) Carapace longer than wide,

regions well defined, smooth on anterior part, with tubercles on posterior part. Grooves deep; carapace flattened longitudinally and moderately vaulted transversely. Orbits flattened, short, distinctly bordered, narrowing posteriorly. Mesogastric region with posterior gastric muscle scars.

Mesogastric groove tubercles present. Molting lines similar to linea homolica present.

Material Examined

Czech Republic. Štramberk (Tithonian): holotype BSP AS III 309 .

Austria. Ernstbrunn (Tithonian of Waschberg Zone): NHMW 1990/0041/3295; NHMW 1990/ 0041/4051.

Dimensions. Dimensions of specimens are given in Schweitzer and Feldmann (2008, p. 279, table 1).

Discussion. Schweitzer and Feldmann (2008) assigned two specimens from Ernstbrunn to L. sublaeve , although their characters distinctly differ from the holotype. Specimens NHMW 1990/0041/ 4051 and NHMW 1990/0041/3295 ( Figure 6 ; Schweitzer and Feldmann, 2008, figure 1.10, 1.11) are very similar to L. fraasi because their groove pattern on both sides of the mesogastric region and transverse grooves between the cervical and branchiocardiac grooves are alike. They have a short rostrum, shortened epigastric regions, and the ornamentation on the posterior part of the carapace is similar.

There is a difference between the holotype of L. fraasi ( Figure 6C, F ) and one of the specimens from Ernstbrunn; specimen NHMW 1990/0041/ 3295 ( Figure 6A, D ) has a smaller posterior part of the mesogastric region, opposite to specimen NHMW 1990/0041/4051 ( Figure 6B, E ), but given all other matching characters we consider both specimens to represent L. fraasi .

There is a molting line similar to a linea homolica visible on specimen NHMW 1990/0041/ 4051 ( Figure 6B, E ). This specimen presents a complete carapace and the molting line is shaped similar as in L. leave ; on the dorsal part of the branchial and epibranchial regions, it is not reaching the anterior margin, but it is directed to the ventral surface of the carapace on the level of the cervical groove. Patrulius (1966) also mentioned the presence of a linea homolica on the specimens of L. laeve and L. fraasi . This view was supported by Wright and Collins (1972) and Collins and Wierzbowski (1985).

Figures

FIGURE 1. Stratigraphic range of the species herein considered within Laeviprosopon with schematic drawings of all the species.

FIGURE 6. Laeviprosopon fraasi A - NHMW 1990/0041/3295, Ernstbrunn; B - NHMW 1990/0041/4051, Ernstbrunn; C - holotype, BSP AS III 309, Štramberk; D - NHMW 1990/0041/3295; E - NHM W1990/0041/4051; F - holotype, BSP AS III 309. Orbital margin marked with an arrow. lh – linea homolica. Scale bars equal 1.0 mm.