Laeviprosopon laeve (von Meyer, 1860)

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 : 5-7

publication ID	https://doi.org/ 10.26879/1204
publication LSID	lsid:zoobank.org:pub:C7630846-28CE-4F22-90FE-F970ACE300BA
persistent identifier	https://treatment.plazi.org/id/DA645246-FF92-FFB9-FED5-EADDF0EFFA4E
treatment provided by	Felipe
scientific name	Laeviprosopon laeve (von Meyer, 1860)
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Treatment

Figures 1 View FIGURE 1 , 3 View FIGURE 3 , 4 View FIGURE 4 , 5 View FIGURE 5

1857 Prosopon laeve von Meyer , p. 556.

1860 Prosopon laeve von Meyer, 1857 . – von Meyer, p. 209, pl. 23, figure 21.

1895 Prosopon laeve von Meyer, 1857 . – Remeš, p. 202, pl. 12, figure 14.

1966 Laeviprosopon laeve (von Meyer, 1857) . – Patrulius, p. 506, figure 2a, 4, pl. 30, figure 7.

1985 Laeviprosopon laeve (von Meyer, 1857) . – Collins in Collins and Wierzbowski, p. 86, pl. 4, figure 3-3.

2008 Laeviprosopon laeve (von Meyer, 1857) . – Schweitzer and Feldmann, p. 277, figure 1.1-1.5.

2018 Laeviprosopon sublaeve (von Meyer, 1857) . – Schweigert and Kuschel, p. 19, figure 8.

Diagnosis. (After Schweitzer and Feldmann,

2008, emended). Species reaching relatively large size (length of mesogastric region of largest specimen is 16.1 mm). Carapace longer than wide, rectangular, strongly vaulted transversally and moderately vaulted longitudinally; cuticle smooth or covered with small granules. Rostrum trifid. Orbit flattened, short, distinctly bordered, with a suborbital spine. Mesogastric region with two gastric spines and posterior gastric muscle scars posterior to these spines. Mesogastric groove tubercles present. Anterior part of carapace and epibranchial region convex, branchial region flatter. Molting lines similar to linea homolica present.

Type material. Laeviprosopon laeve was described by von Meyer in 1860 based on two specimens which are both lost (Schweitzer and Feldmann, 2008). They have been collected from the Kimmeridgian locality Oerlinger Tal in Germany. Herein we describe new material from the upper Kimmeridgian locality Bad Überkingen-Oberböhringen , which is stratigraphically close to the Oerlinger Tal locality. Therefore, we assign a neotype: specimen SMNS 70527 About SMNS /1.

Material Examined

Austria. Ernstbrunn (Tithonian of Waschberg Zone): NHMW 1990/0041/3309; NHMW 1990/ 0041/3834; NHMW 1990/0041/4915; NHMW 2007z0149/0020; NHMW 2007z0149/0021; NHMW 2007z0149/0022.

Poland. Rudniki (lower Kimmeridgian, planula Zone): IGPUW /C/1/128, Niwiska Dolne (lower Kimmeridgian, planula Zone): IGPUW /C/1/129.

Germany. Bad Überkingen-Oberböhringen ( upper Kimmeridgian ) : SMNS 70527 About SMNS / 1 - neotype, SMNS 70527 About SMNS /2, SMNS 70527 About SMNS /3, SMNS 70527 About SMNS /4, SMNS 70527 About SMNS /5, SMNS 70527 About SMNS /6, SMNS 70527 About SMNS /7, SMNS 70527 About SMNS /8, SMNS 70527 About SMNS /9, SMNS 70527 About SMNS /10, SMNS 70527 About SMNS /11.

Poland. Bzów (middle Oxfordian): I-F/ MP /3663/ 1533/08; I-F/ MP /3914/1533/08; I-F/ MP /4627/1534/ 08.

Niegowonice (middle – upper Oxfordian): I-F/ MP / 915/1507/08; I-F/ MP /3245/1532/08; I-F/ MP /3295/ 1532/08; I-F/ MP /4810/1534/08; I-F/ MP /5467/1543/ 09; I-F/ MP /6275/1599/12.

Ogrodzieniec (lower – middle Oxfordian): I-F/ MP / 172/1489/08.

Dimensions. The state of preservation of the material from the ISEA collection is not good enough to take measurements of all specimens. The length of the mesogastric region of the smallest specimen is 3.6 mm and that of the largest one 8.8 mm. The length of the mesogastric region of specimen SMNS 70527/1 is 5.4 mm, 4.0 mm for SMNS 70527/4, and 4.45 mm for SMNS 70527/2. Total length without rostrum is 12.0 mm in the specimen SMNS 70527/1, 9.1 in the specimen SMNS 70527/4 and 10.3 mm in the specimen SMNS 70627/2. The width at the hepatic region is 9.2 mm in the specimen SMNS 70527/1.

Emended description. As a large number of new specimens show characters not known before, a redescription is needed.

The carapace is longer than wide, strongly vaulted transversally and moderately vaulted longitudinally, widest in the hepatic region. The rostrum is well preserved only for 2007z0149/0022, showing three spines, of which the middle one is the longest and directed downwards. There is only a forked base of the rostrum visible in SMNS 70527/ 8 ( Figure 4C View FIGURE 4 marked with black arrows). There are distinct spines situated laterally from the rostrum ( Figure 4D, H View FIGURE 4 ).

The anterior groove is visible in the intersection of the rostrum and the upper orbital margin. The epigastric regions are rounded. The mesogastric region is distinctly bordered by mesogastric grooves; the length of its anterior (narrow) part is about 0.59 of the posterior (wide) part; the separation between these parts is marked by an incision. The posterior gastric muscle scars are present on the posterior mesogastric region, and in front of them there are two tubercles ( Figure 4 View FIGURE 4 E-G). Mesogastric groove tubercles are present ( Figure 4E View FIGURE 4 ).

The gastric pits are rounded. The urogastric region is vaulted, with an incision in the center dividing it into two parts ( Figure 4E View FIGURE 4 ). A tubercle on the urogastric region is very small. Lateral parts of the postcervical groove are connected with the branchiocardiac groove. These grooves bound narrow surfaces anterior to the cardiac region ( Figures 4E View FIGURE 4 ; 5A View FIGURE 5 , D-E).

The cardiac region is distinctly delimited by the branchiocardiac groove. There are two tubercles in the anterior part of this region and one in the posterior part ( Figure 5 View FIGURE 5 A-B, D-E).

The anterior part of the carapace and the epibranchial region are convex, and the branchial region is more flattened. The highest point of the carapace lies in the posterior part of the mesogastric region ( Figure 5 View FIGURE 5 G-H). The grooves are deep and wide, and the cervical groove is the widest. The branchiocardiac groove reaches the posterior margin of the carapace. Few of the specimens from ISEA (I-F/MP/915/1507/08, I-F/MP/54671543/ 09) have almost smooth carapaces with only few tubercles on the steinkern; the cuticle is not preserved. Others from ISEA (I-F/MP/3663/1533/08, IF/MP/3914/1533/08 and I-F/MP/6275/1599/12) have carapaces covered with tubercles ( Figure 4A View FIGURE 4 ). Specimens from Oberböhringen and Ernstbrunn are also covered with tubercles. The cuticle of these specimens is relatively thick, and its surface is covered with tiny pits, each of which corresponds to a tubercle on the steinkern. Pits on the cuticle and corresponding tubercles on the steinkern are also visible on specimen I-F/MP/ 3663/1533/08 ( Figure 4A View FIGURE 4 ). The posterior margin of the carapace is preserved only partially or not at all.

Most specimens from the Polish localities are damaged in the posterior part, but specimens I-F/ MP/39141533 /08, I-F/ MP/6275 /1599/12 ( Figure 5C View FIGURE 5 ), IGPUW /C/1/128 and IGPUW /C/1/129 are showing a loss of lateral parts of the branchial regions. Most specimens from the German locality Oberböhringen are also molts with a molting line similar to a linea homolica ( Figure 5 View FIGURE 5 A-B, D-G). Only one specimen shows an entire, unbroken carapace and the molting line is not visible on it ( Figure 5H View FIGURE 5 ). Molting lines are laying on the dorsal surface of the branchial and epibranchial regions and crossing on the ventrolateral side of the hepatic region ( Figure 5B View FIGURE 5 ) .

Discussion. The new specimens of the type species from the German locality Oberböhringen are crucial for reassessing the systematic placement of Laeviprosopon . These specimens are ascribed to the type species due to their characters which correspond to the original illustration of L. laeve . The overall shape and convexity of the carapace and each region and groove, the presence of gastric muscle scars and the mesogastric groove tubercles are consistent with L. laeve .

There is intraspecific variation visible in the ornamentation of the carapace of specimens from different localities, apparently not related to preservation. There are specimens with and without tubercles on the steinkern in the collection of ISEA PAS. Specimens from Oberböhringen and Ernstbrunn are also covered with tubercles on the steinkern. These tubercles correspond with pits on the cuticle where preserved.

These pits in the cuticle and corresponding tubercles on the steinkern are also present on specimen I-F/MP/3663/1533/08. Because all other characters correspond well with Laeviprosopon laeve , the presence of tubercles is considered to represent intraspecific variation.