Smilium? parvulum ( WITHERS , 1914)

Kočí, Tomáš & Veselská, Martina Kočová, 2013, The First Recorded Occurrence Of Smilium? Parvulum Withers, 1914 (Cirripedia, Thoracica) From The Bohemian Cretaceous Basin (The Czech Republic), Acta Musei Nationalis Pragae Series B 69 (3 - 4), pp. 147-150 : 148

Smilium? parvulum ( WITHERS, 1914)

Text-fig. 3

1851 1912 1914 1935

2013 Scalpellum sp. ; Darwin, p. 21.

Scalpellum sp. ; Withers, p. 231.

Scalpellum parvulum WITHERS ; Withers, p. 496, text-figs 1–6. Smilium (?) parvulum (WITHERS) ; Withers, p. 141, pl. 12, figs 9–15.

Smilium (?) parvulum (WITHERS) ; Kočí and Kočová Veselská, p. 179, figs 1–2.

M a t e r i a l. NM O7133, the single specimen exhibits a minute carina in the palaeontological collections of the National Museum (Prague).

D i s t r i b u t i o n. England – Upper Albian – Cambridge Greensand: locality Cambridge; Lower Cenomanian – Chalk Marl, Schloenbachia varians Zone : localities Cambridge, Burham and Kent ; Upper Turonian – Plesiocorys plana Zone : localities Alton District , Hampshire .

Czech Republic – Lower Turonian –? Mytiloides labiatus Zone : Velim.

D e s c r i p t i o n. The umbo is removed from the apex by about one-third the length of the carina. The uppermost third of this plate is rounded with welldeveloped longitudinal ridges on the tectum. Parieties, lateral sides with distinct transversal lines, are developed in the lower two thirds of the plate. The internal lateral sides, intraparieties, form an elongation of the plate and give it a tapered beaked shape. Incremental growth lines are fine and distinct. The inner surface is smooth without growth lines. The carina length equals 4 mm and the width at its basal edge is 1.4 mm.

R e m a r k s a n d r e l a t i o n s h i p s. Withers (1935) mentioned and described only four specimens of minute carina of Smilium? parvulum from the Cenomanian of England. These carinae are of exceptionally minute size. Because all the carinae are of the same small size, it indicates that they belong to adult specimens. Withers (1928) noted that some specimens of the Cenomanian species Arcoscalpellum lineatum (DARWIN) show a slight tendency for the intraparieties to extend a little beyond the umbo, but there is no relationship with the Cenomanian Smilium? parvulum . Withers (1928, 1935) mentioned an identical tendency in the Upper Senonian species Scalpellum hagenowianum BOSQUET , and Scalpellum beisseli BOSQUET et MÜLLER from the Middle and the Upper Senonian of England ( Micraster coranguinum Zone , Upper Coniacian – Lower Santonian; Belemnitella mucronata Zone , Upper Campanian – Lower Maastrichtian) and in the Maastrichtian species Scalpellum gabbi PILSBRY , Scalpellum darwinianum BOSQUET , Scalpellum hagenowianum BOSQUET and Scalpellum ryckholti WITHERS from Belgium, the Netherlands and the United States of America. These scalpellid species were recently placed in the genus Virginiscalpellum WITHERS, 1935 . Smilium? parvulum is distinguished from the aforementioned species of Virginiscalpellum on the basis of a less complex structure of carina. The umbo of the genus Virginiscalpellum is closer to the apex than in the genus Smilium . In the Cenomanian–Turonian species Smilium? parvulum WITHERS , extant species Smilium peronii GRAY (see Withers 1953: 170, fig. 69) and extant species Euscalpellum rostratum (DARWIN) , the carinae run straight from the base to the umbo, and the umbo has moved from the apex along the carina, about one-third of the way down its length (see Withers 1953:173, fig. 75).

Figures

Text-fig. 3. Smilium? parvulum (WITHERS, 1914), carina, specimen NM O7133, 1 – outer view of carina with umbo under apex, 2 – lateral view of carina, 3 – inner view of carina with remains of claystone after preparation. Specimen is to scale.