Catherinum anglicum, Gale, 2016

Gale, Andrew Scott, 2016, Phylogeny of the deep-sea cirripede family Scalpellidae (Crustacea, Thoracica) based on shell capitular plate morphology, Zoological Journal of the Linnean Society 176 (2), pp. 266-304 : 301

CATHERINUM ANGLICUM SP. NOV.

FIGURE 19C–K, N–Q, T, V

Diagnosis

Catherinum in which the occludent margin of the tergum is straight, and the external surface adjacent to this carries three ribs that diverge from the umbo. The upper part of the upper latus margin of the scutum is embayed. The carinolatus has a very broad upper latus margin.

Derivation of name

After East Anglia , in which the type material was collected .

Material

Fifty valves, including carinae, scuta, terga, and carinolatera, from the upper Campanian , Belemnitella mucronata zone chalk of Keswick and Cringleford Newfound Farm pits, Norwich, Norfolk, UK. The scutum illustrated is the holotype ( Figure 19O ) , and the other illustrated valves are paratypes.

Description

The carina ( Fig. 19E, I, P, T, V ) is gently incurved towards the tergum, and the parietes are of even width; intraparietes are not developed. The tectal ridges are robust and broad ( Fig. 19E, T ), and the tectal surface between these is slightly convex. The tergum ( Fig. 19Q ) is elongated and triangular, and the carinal margin is slightly convex. Three radial ridges run from the umbo, subparallel with the occludent margin. The scuta ( Fig. 19J, K, N, O ) are concavo–convex, trapezoidal, and the umbo is pointed and incurved; the upper latus margin has a distinctive concavity just beneath the tergal–upper latus angle. A narrow groove runs parallel with the occludent margin. On the interior of the valve, a deep, oval dwarf male receptacle lies between the apex and the scutal adductor scar. The carinolatus ( Fig. 19C, D, F–H ) has a low, incurved umbo, and a tall carinal margin. The long, straight upper latus and inframedian latus margins are set at right angles. The plate is very typical of Catherinum of the Ca. hispidum ( Fig. 19A, B ) and Ca. striolatum ( Fig. 7P, Q ) type.

Remarks

Catherinum anglicum sp. nov. is perhaps closest to the extant Ca. hispidum from the Norwegian Sea. The carinae are very similar indeed, both carrying very broad, robust tectal ridges ( Fig. 19I, S, T ), and with shallow short grooves for articulation with the carinolatus in the interior ( Fig. 19U, V ). The terga are similar in shape, but the scutal margin is convex in Ca. hispidum and straight in Ca. anglicum sp. nov. Three divergent ribs run from the umbo, adjacent to the occludent margin in Ca. anglicum sp. nov., but these are absent in the living species ( Fig. 19Q, R ). The scuta both possess an incurved umbo, and a large, deep pit for dwarf males ( Fig. 19J–O ), which is directed slightly more transversely in Ca. hispidum . The carinolatera are similar in shape ( Fig. 19A–D, F–H ), but the tergal margin is longer in Ca. anglicum sp. nov. It can be distinguished from small carinae of Diotascalpellum fossula by the absence of intraparietes. A further undescribed species of Catherinum is present in the Norwich chalk assemblage; this will be named subsequently.

This is a very small species: the scuta have a maximum height of 2 mm, and the total height of the individuals was probably not more than 5 mm. It was possibly attached to living crustaceans or pycnogonids, by analogy with the small extant species Weltnerium nymphocola ( Hoek, 1883) and Verum brachiumcancri Weltner (see Buhl-Mortensen & Høeg, 2012).

Figures

Figure 7. Evolution of lateral plate morphology, dorsal side: A–E, Weltnerium stroemii (M. Sars, 1859); F–J, Weltnerium nymphocola (Hoek, 1883); K–O, Catherinum novazelandiae (Hoek, 1883); P–T, Catherinum striolatum (G.O. Sars, 1877); U–Y, Amigdoscalpellum rigidum (Aurivillius, 1898). External aspect of carinolatus (A, F, K, P, U); interior of carinolatus (B, G, L, Q, V); external view of inframedian latus (C, H, M, R, W); dorsal (carinal) view of basal capitulum (D, I, N, S, X); enlarged lateral view of basal capitulum (E, J, O, T, Y). Note the changes in the nature of the articulation between the carinolatera of a pair (interpenetrant, X; opposed double articulation, D, I, N, S) and those in the shape of the inframedian latus (triangular, W; waisted hourglass, M, R; pentagonal, C, H). See Table 1 for details of localities. Scale bars: A–C, F–H, M, P-R, U–V, 0.5 mm; D, E, I, J, N, O, S, T, X, Y, 1 mm.

Figure 19. Fossil and recent Catherinum. C–K, N–Q, T, V, Catherinum anglicum sp. nov., Upper Campanian, Belemnitella mucronata zone, Keswick, Norwich, UK; (O) is the holotype, the other specimens are paratypes. C, D, F, G, carinolatera in external (C, D, F) and internal (G, H) aspects (C, NHMUK IC 1203; D, 1204; F–G, 1206; H, 1208). E, transverse section of carina (NHMUK IC 1205); I, T, dorsal view of carinae (NHMUK IC 1209, 1216); P, lateral view of carina (NHMUK IC 1214); V, internal view of base of carina (NHMUK IC 1217); J, K, O, internal views of scuta, to show large pit for dwarf males (NHMUK IC 1210, 1211, 1213); N, external view of scutum (NHMUK IC 1212); Q, external view of tergum (NHMUK IC 1215). A, B, L, M, R, S, U, Catherinum hispidum (G.O. Sars, 1890). Recent, Norwegian Sea. A, B, carinolatus in external and internal views. L, M, external and internal views of scutum. R, external view of tergum. S, U, dorsal and internal views of carina. Scale bars: S, U, V, 1 mm; A–D, F, G, K–O, Q, R, T, 0.5 mm; E, H, P, 0.2 mm.