Stramentum (Stramentum) pulchellum (G.B. SOWERBY JR., 1843)

Veselská, Martina Kočová, Kočí, Tomáš & Buckeridge, John, 2013, A Systematic Revision Of Stramentum (Stramentum) Pulchellum (G. B. Sowerby Jr., 1843) (Cirripedia, Thoracica, Stramentidae) From The Bohemian Cretaceous Basin, The Czech Republic, Acta Musei Nationalis Pragae Series B 69 (3 - 4), pp. 151-158 : 153-155

Stramentum (Stramentum) pulchellum (G.B. SOWERBY JR., 1843)

Pl. 1, figs 1–9

1843 Loricula pulchella ; G. B. Sowerby jr., p. 260.

1851 Loricula pulchella ; Darwin, p. 81.

1878 Loricula gigas FR. ; Frič, p. 147.

1880 Loricula gigas FR. ; Frič, p. 137.

1885 Loricula gigas FRIČ ; Kafka, p. 21, pl. 3, fig. 5.

1886 Loricula gigas FRIČ. ; Kafka, p. 573.

1887 Loricula pulchella, SOW. ; Fritsch and Kafka, p. 1 (including var. minor and var. gigas ).

1889a Loricula pulchella, SOW. var. gigas, FR. ; Frič, p. 96.

1889b Loricula pulchella, SOW. var. gigas, FR ; Frič, p. 90.

1920 Stramentum pulchellum, G. B. SOWERBY, JUN. , sp.; Withers, p. 70.

1935 Stramentum pulchellum (G. B. SOWERBY, JUN.) ; Withers, p. 316.

1977 Stramentum pulchellum (SOWERBY) ; Hattin, p. 812.

1986 S. pulchellum (G. B. SOWERBY JR) ; Collins, p. 130.

1989 Stramentum pulchellum (SOWERBY) ; Oekentorp, p. 134, pl. 1, fig. 1; pl. 2, figs. 3– 4; pl. 4, figs. 1, 4.

1993 Stramentum pulchellum (G.B. SOWERBY JUN., 1843) ; Breton and Boiné, p. 20.

1994 Stramentum (Stramentum) pulchellum (SOWERBY) ; Hauschke, p. 15, pls. 1– 5.

1996 Stramentum (S.) pulchellum ( SOWERBY 1843) ; Wittler, p. 94.

2011 Stramentum (Stramentum) pulchellum ( SOWERBY, 1843) ; Ifrim et al., p. 527.

2011 Stramentum (Stramentum) pulchellum (SOWERBY) ; Hauschke et al., p. 202, figs. 3– 5.

2012 Stramentum (Stramentum) pulchellum (SOWERBY) ; Schöllmann and Hauschke, p. 64, fig. 5; taf. 1, figs. 1– 7.

H o l o t y p e. A specimen from the Turonian (Upper Chalk) at Rochester, England; described and illustrated by G. B. Sowerby jr. (1843); in the collections of the Natural History Museum (London), registration number NHM 59150.

M a t e r i a l. A total of eight specimens; NM O3445 – O3449, NM O4255 and NM O 7132 in the palaeontological collections of the National Museum (Prague) and PA 1476 at Krupka Museum. With the exception of NM O3448, NM O7132 and PA 1476, these represent Fritsch’s (1877) and Fritsch and Kafka’s (1887) originals. NM O3445 – O3447, NM O3449, NM O4255 and NM O7132 were recorded as epizoans on shells of Lewesiceras or Collignoniceras . The original substrate of NM O3448 and PA 1476 is uncertain. All ontogenetic stages, from juvenile to adult, are presented and all individuals are (semi-) articulated.

D i s t r i b u t i o n. Cenomanian of England, France and northwest Germany; Turonian of northern Ireland, England, northwest Germany and the Czech Republic; Coniacian of Mexico;?lower Campanian of northern Germany ( Jagt 2013). For summaries of geographical and stratigraphical distribution, reference is made to Hauschke (1994), Nomura et al. (2009), Ifrim et al. (2011), Hauschke et al. (2011) and Schöllmann and Hauschke (2012). Specimens from the BCB originate from the Lower-Upper Turonian, as follows: Lower to Middle Turonian (Bílá Hora, Prague: NM O3446, NM O3447; Středokluky: NM O3449; Peruc vicinity NM O7132; Džbán: NM O3448, see below), Upper Turonian (Koštice: NM O3445, with negative imprint NM O4255; Lahošť: PA 1476).

D i a g n o s i s. Tergum triangular with growth lines sharply upturned (near occludent margin); scutum triangular with umbo removed from apex by between one quarter to one third the length of the plate; ventro-apical (occludent) margin straight or gently convex; carinolatus with growth lines sharply upturned along tergal margin; upper latus triangular; peduncular plates arranged in eight vertical imbricating rows: six broad rows aligned beneath and of about the same width as the carinolatera, upper latera and scuta; two narrower rows aligned beneath the carina and rostrum; rostrum is not preserved.

D e s c r i p t i o n. All specimens conform broadly to the species; PA 1476 differs slightly in scutal and upper lateral outline. Individuals expose external surfaces of capitular and peduncular plates, representing either left-hand (NM O3445, NM O3446) or right-hand sides (NM O3447 – O3449, NM O7132, PA 1476). NM O4255 represents an internal mould of NM O3445. Rostrum not preserved (it may seem that a rostral fragment is preserved in NM O7132, but a small piece placed on the connection of the occludent and basal margin is only a broken part of a scutum).

Capitulum about one third length of peduncle. Scutum subtriangular with convex occludent margin, growth-lines sub-parallel to basal margin, then sharply upcurving to parallel upper lateral margin; scutal umbo removed from apex by about one quarter to a third the length of occludent margin. Upper latus almost isosceles-triangular in outline, length comparable to scutum; growth-lines parallel to basal margin. Tergum broadly triangular with acute occludentupper lateral angle, carinolateral margin straight to slightly convex, apex acute and level with that of carinolatus; growth-lines parallel upper lateral margin, but upturn sharply to run sub-parallel to occludent margin; basal angle of tergum extends to just above the capitulum-peduncle boundary. Carinolatus obliquely triangular with growth lines parallel to a straight or gently convex basal margin. Carina narrow and long triangular slightly convex with length comparable to carinolatus.

Peduncle. Heavily calcified, joining capitulum obliquely and sloping gradually towards rostral side, widest at one third of length (measured from base of capitulum) narrowing towards base and capitulum, with size of single plates decreasing. Arranged with three broad vertical rows aligned with paired scuta, upper latera and carinolatera and two narrower, unpaired outer rows (rostral and carinal). All plates with fine growth lines parallel to plate outline; plates of scutal, upper lateral and carinolateral columns of similar size, becoming narrower, towards both capitulum and the base. Shape of scutal and carinolateral columns broadly sub-trapezoidal, straight or gently convex on rostral and carinal sides, plates of upper lateral column broadly sub-hexangular with convex upper margin and concave lower margin (more markedly than in adjacent columns), plates narrower just below capitulum and with near-straight upper margins; width about four times height. Carinal plates almost quadrangular, slightly higher than wide and slightly less than four times width of corresponding plates in adjacent column. Plates of rostral column rather subtrapezoidal; of similar size to carinal row, but broader in width; towards base, plates become narrower and scutal margin straightens. Outer plates overlap neighboring inner plates; row of plates corresponding to upper latus overlapped from both sides. Within each row, overlapping occurs from base to top. Basal plates of peduncle not preserved.

Lot NM O3445 contains two specimens, the upper one preserving only scutum, upper latus and a deformed tergum; occludent margin in both capitula straight, peduncle is almost complete, lacking solely lower part of carinal column, lower specimen lacks rostrum, carina and lower half of peduncle, uppermost plates of carinolateral and scutal columns are sub-hexangular as in upper lateral column; plates of rostral column have convex upper margins and heavier growth lines.

NM O3446 has a fragmentary part of the right-hand side scutum exposed; tergum longer than carinolatus and carina and tergum exceeding both; plates in rostral column about twice width of those in carinal column; peduncle almost complete, lacking only lowest part of each column.

NM O3447 lacks rostrum, carina and apex of a rounded and deformed tergum, occludent margin straight; three main columns of peduncle complete, rostral column and most of carinal column not preserved.

Lot NM O3448 represents some juvenile individuals as external moulds; very small juveniles have about 6-8 plates in peduncular columns, most of them preserved only as fragments of capitulum or peduncle; a single specimen almost complete, capitulum without carina and rostrum and peduncle with three main columns (scutal, upper lateral, carinolateral) corresponding to description above; occludent margin of capitulum straight.

NM O3449 capitulum incomplete (rostrum, scutum and rostral and scutal column of peduncle lost); scutal margin of upper latus broken; remaining part of occludent margin straight, only upper lateral, carinolateral and carinal columns preserved, all lacking lower parts; size and shape of two main columns similar, upper plates narrowest; towards base, plates of carinolateral column rather broadly subtrapezoidal as in other specimens, lower plates of carinal column with spurs on both sides and with convex upper and lower margins (rhomboidal outline), connection of upper lateral and carinolateral columns disarticulated; slight deformation displaced upper lateral margin towards carinolateral row.

Lot PA 1476 comprises two specimens, the upper (smaller and younger) lacking rostrum, tergum and upper parts of scutum and upper latus; peduncle almost complete, lacking only lower part; rostral column disarticulated; the lower specimen (larger and more mature) lacking only rostrum and apex of tergum; specimen retaining part of second scutum from left-hand side as in NM O3446; scutum and upper latus slightly deformed, scutum with strongly convex upper lateral margin (vs straight in other specimens) and outline less rounded-triangular and upper latus with concave scutal margin. This results from slight disarticulation of some peduncular plates (N. Hauschke, pers. comm., 2012). Occludent margin convex (because of lack of uppermost part of tergum and almost rounded scutum), upper lateral and rostral columns nearly complete, only few plates of carinal column and upper half of carinolateral and scutal columns present; upper and lower margins of scutal and carinolateral plates almost straight, towards base, plates of rostral column rhomboidal (with spur on both sides) rather than subtrapezoidal.

R e m a r k s. All material, collected near the end of the nineteenth century, is articulated or semi-articulated (e.g., PA 1476) and well preserved. NM O3445 (and counterpart NM O4255), NM O3446, NM O3447, NM O3449 and NM O7132 were found as epizoans of body chambers of ammonite shells. We are not certain about the original substrate of NM O3448 and PA 1476. NM O3448, which represents external moulds of juvenile individuals and was recorded by Fritsch and Kafka (1887) as an epizoan of Collignoniceras woollgari . As noted, the original has been replaced with other juveniles in a similar state of preservation. Fritsch’s original stems from the Lower-Middle Turonian calcareous marlstones from a defunct quarry in the Džbán Plateau; he differentiated three growth stages – on the basis of the number of peduncular plates; all individuals have four capitular plates preserved: scutum, upper latus, tergum and carinolatus. NM O3448 also comprises juveniles, but unfortunately, information on either the substrate or provenance area is lacking, but we assume them to have come from Džbán as well. One of the juveniles is nearly complete, having four capitular plates and 6-8 plates in each peduncular column. Others also have four capitular plates, but due to their fragmentary preservation it is impossible to distinguish growth stages. It cannot be determined whether specimens in lot NM O3448 were attached or not, but in view of the good state of preservation, it is most likely that these juveniles were also attached to some shell. A similar case is PA 1476, which also comprises two well-preserved stramentids, although it is not clear what were originally attached to. Only small pieces of matrix survive with these collections.

Fritsch and Kafka (1887) described two varieties of Stramentum pulchellum from the BCB, namely minor and gigas , on the basis of differences in peduncular plates and overall body size. Var. gigas was recorded to have pointed plates in the carinal column (reflecting rapid growth of the body), with plates of the carinolateral and scutal columns broadly subtrapezoidal and produced into a spur on the upper lateral sides, and plates of the upper lateral column equally developed on the upper lateral and scutal sides and all plates of the three main columns have rounded margins. However, these features are typical of all Czech stramentids. Individuals of var. gigas are also larger, reflecting older age and these have a greater number of peduncular plates. Fritsch’s var. minor comprised six specimens of 15 to 20 mm in size, all from the Lower-Middle Turonian; unfortunately, only three of these survive (NM O3446, NM O3447 and NM O3449). NM O3446 was described as an epizoan of the body chamber of a juvenile Lewesiceras peramplum ; it is the largest and best preserved of individuals of var. minor . The substrate of NM O3447 was Collignoniceras woollgari , while the deformed NM O3449 was fixed on L. peramplum . All individuals are from the Lower-Middle Turonian. NM O3445 comprises two stramentids, originally described by Fritsch and Kafka (1887) as var. gigas , as epizoans on the body chamber of a large L. peramplum . PA 1476 is of the Upper Turonian age. In short, any preferred orientation and position of attached stramentids cannot be recognised, contrary to other Cretaceous stramentids described by Breton and Boiné (1993), Hauschke (1994), Wittler (1996), Hauschke et al. (2011), Ifrim et al. (2011) and Schöllmann and Hauschke (2012).

Finally, it should be stressed that the figures and animal restorations (drawings) presented in works by Fritsch (notably in Fritsch and Kafka 1887) often do not fully correspond with the original specimens (pers. obs. MKV, TK) as in many cases his reconstructions are idealised. This is especially true for stramentids NM O3446 (figured in Fritsch and Kafka 1887: pl. 1, fig. 2) or NM O3449 (figured in Fritsch and Kafka 1887: pl. 1, fig. 4). Thus, caution must be taken when dealing with Frič’s taxa on the basis of published figures only.