Vibrissalana, 2019

Robins, Cristina M. & Klompmaker, Adiël A., 2019, Extreme diversity and parasitism of Late Jurassic squat lobsters (Decapoda: Galatheoidea) and the oldest records of porcellanids and galatheids, Zoological Journal of the Linnean Society 187, pp. 1131-1154 : 1141-1142

VIBRISSALANA ROBINS & KLOMPMAKER GEN. NOV.

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Type species: Vibrissalana jurassica Robins & Klompmaker sp. nov. by monotypy.

Diagnosis: As for species.

Etymology: A combination of the Latin vibrissa, whisker, and lana, wool. The carapace of the sole species of this genus bears setal pits.

Discussion: Most representatives of galatheoid families differ from Vibrissalana in several aspects. Munidopsids tend to be longer than wide (without rostrum), with some about equally wide as long, have more regional definition for most species and usually exhibit a keeled rostrum (e.g. Ahyong et al., 2010; Macpherson & Baba, 2011; Robins et al., 2013). Paragalatheids are convex; most of them widen substantially toward the posterior, and they are typically longer than wide (without rostrum; Robins et al., 2016). Representatives of Catillogalatheidae are longer than wide (excluding rostrum) and subrectangular (although some are nearly as wide as long), and most of them have a keeled rostrum ( Robins et al., 2016). Munidids have transverse ridges, a trifid rostrum, a carapace that is longer than wide (excluding rostrum) or equally wide as long, and often bear spines on the dorsal carapace (e.g. Ahyong et al., 2010; Macpherson & Baba, 2011; Robins et al., 2012). Most galatheids have transverse ornamentation, are usually longer than wide, with some about as wide as long, and the triangular rostrum often bears small spines ( De Angeli & Garassino, 2002; Ahyong et al., 2010; Macpherson & Baba, 2011). Conversely, the wider than long carapace (excluding rostrum), ovate appearance, the seemingly short flank, the wide rostrum with its axial groove, the flattened carapace, limited ornamentation and a poorly developed groove pattern are most consistent with placement of Vibrissalana in Porcellanidae , and these characters fit several diagnoses of Porcellanidae ( Ahyong et al., 2010; Schweitzer & Feldmann, 2010b, 2012). Regarding the ovate appearance of Vibrissalana , the right lateral part is not preserved posteriorly, but the course of the posterior margin curving somewhat forward suggests that the missing part is unlikely to be straight but is curved instead, as in many porcellanids (e.g. De Angeli & Garassino, 2002: pl. 7.3; Beschin et al., 2016: pl. 4.5). This reasoning applies even more so to the anterolateral margin, which is better preserved. Given that only one incomplete specimen is known, placement in Porcellanidae is tentative, but until new material is available that suggests otherwise, we consider this taxon to represent the oldest known porcellanid in the fossil record.

Below, we compared Vibrissalana with exclusively fossil genera and modern genera with a fossil record. Unlike Vibrissalana , the carapace of Beripetrolisthes widens posteriorly and the lateral margins of the carapace bear spines. The carapace of Cretacolana is more ovate, widening substantially posteriorly. The preserved portions of the lateral margins of Vibrissalana indicate that this genus does not widen posteriorly. Eopetrolisthes bears transverse ridges on the dorsal carapace and bears one spine on the lateral margin near mid-length. Lobipetrolisthes bears spines on the lateral margins. Disipia exhibits transverse striae on the posterior carapace and shows some spines on the anterior part of the lateral margin. Longoporcellana lacks distinct grooves. Muelleristhes does not have a groove branching off the cervical groove near the axial part, and the epigastric swellings are oriented more obliquely. Pachycheles has a much more downturned rostrum, and the cardiac region is positioned immediately posterior to the cervical groove. Today, Petrolisthes is a diverse and probably heterogeneous genus with variable carapace ornamentation (e.g. Haig, 1960); therefore, we focus primarily on comparisons to the type species, Petrolisthes violaceus ( Guérin, 1831) . The cardiac region of extant members of this genus tends to be positioned directly posterior to the axis of the cervical groove rather than separated by the uro-metagastric region, and the rostrum appears to be more downturned in comparison to Vibrissalana . Paraporcellana exhibits a rostrum without a distinct axial groove and bears spines on the lateral margin. The lateral margin of Pisidia bears spines. Polyonyx is usually much wider than long and bears a strongly downturned rostrum. Porcellana appears to have a three-pronged rostrum, not visibly preserved in Vibrissalana . Spathagalathea exhibits transverse ridges and appears to have a much more pronounced rostrum.

VIBRISSALANA JURASSICA ROBINS & KLOMPMAKER