Bothriolepis panderi Lahusen, 1880

Lukševičs, Erwin, 2001, Bothriolepid antiarchs (Vertebrata, Placodermi) from the Devonian of the north-western part of the East European Platform, Geodiversitas 23 (4), pp. 489-609 : 519-521

Bothriolepis panderi Lahusen, 1880

( Figs 12 ; 21J )

Bothriolepis panderi Lahusen, 1880: 137 , taf. 1, figs 1- 5; taf. 2, fig. 1 [non Figs 2-4 ]. — Gross 1932: 25 (in part).

LECTOTYPE. — The complete head shield and anterior part of the trunk armour MM 1/96, chosen by Gross (1932).

MATERIAL EXAMINED. — SMNH P.3387, CD1; MM 2/96, 3/96, fragments of the pectoral fin; LDM 63 /337, AVL, 63/338, ADL ; GM 1/119, 2/119, 7/119, fragments of AVL, 8/119 and 9/119, pieces of pectoral fin bones. These bones and lectotype is all so far available material .

LOCALITY AND HORIZON. — Right bank of Syas’ River not far from Montsevo village, Russia; the lower Frasnian Snetnaya Gora Beds.

DIAGNOSIS. — Bothriolepis with a median dorsal trunk armour length of at least 125 mm. B/L index of the head shield is 147. Rostral margin is convex, much shorter than the posterior margin. Orbital fenestra is relatively small, short and broad, with a B/L index 180. Prm is relatively broad, B/L index is 100; the slightly convex orbital margin is much shorter than the rostral margin. Rostral plate is twice as broad as it is long and bears deep and short nasal notch. Pineal plate is relatively broad with the concave anterior and lateral margins; the posterior margin is almost stright. Outer surface of the plate is pierced by the pineal opening. Nu relatively broad, L/B index of 61. Pmg is longer than broad with lateral margin much longer than the median margin. Trunk-armour is relatively broad, with somewhat elevated dorsal wall. AMD is moderately broad, B/L index about 71. The anterior margin is moderately broad, 1.5 time shorter than the maximum breadth of the plate. The postlevator processes are strongly defined. Median dorsal ridge poorly developed. AVL is of moderate breadth with short subcephalic division; the anterior lateral corner of subcephalic division is situated in the middle between the median and lateral margins. Proximal segment of the pectoral appendage is relatively long and slender, about five times as long as it is broad; it bears prominent lateral and mesial spines, the mesial ones are numerous, short and closely setting. CD1 of moderate size, L/B index about 2.6. The ornamentation consists of tubercles and short vermiculated ridges both on the head-shield and the trunkarmour.

DESCRIPTION

Bothriolepis panderi attained a somewhat larger size than B. cellulosa . The length of the head shield reaches about 60 mm, the dorsal length of the trunk armour is estimated at least about 125 mm. The proportions and shape of the head-shield resemble that of B. canadensis , but differs well from that in B. cellulosa . It is comparatively flat in its anterior part and slightly vaulted in the posterior part. It seems to be relatively shorter than that in B. cellulosa .

In almost all aspects, the Prm looks similar to that in B. cellulosa and B. canadensis . It is broadest at the infraorbital sensory groove or rostral margin. The orbital margin seems to be devoid the nasal notch. The rostral margin is not wellpreserved in the lectotype and hence it is impossible to decide whether or not the rostral angle is presented.

The La on the both sides of the lectotype are crushed and therefore do not show several characters. The rostral margin seems to be of moderate breadth. The infraorbital sensory groove crosses the plate not far from its lateral and rostral margins. The central sensory line groove is finished slightly anteriorly the level of middle of the orbital fenestra length.

The Ro is much broader and shorter than in B. canadensis . The Pi is relatively broad, breadth slightly exceeds a length. The Pp is short and broad, L/B index is 156, with a slightly convex anterior margin.

The Nu is deficient posteriorly, but seems to be relatively broad with a L/B index of about 61. The anterior division of the lateral margin is concave and a little shorter than the posterior division. There are short supraoccipital grooves, which terminate little in front of the obtected nuchal area at the rather large external openings for the endolymphatic ducts.

The Pn is of moderate breadth, L/B index 82. The lateral division of the Pn is relatively narrow and is composing 49% of the general breadth of a plate.

Three sclerotic plates in most features are similar to that of B. canadensis ( Stensiö 1948: textfig. 21).

The dorsal wall of the trunk armour is higher than that in B. cellulosa . The median dorsal ridge is rather weakly developed, and both dorsolateral and ventro-lateral ridges are well-marked. The anterior margin of the AMD is weakly convex. The antero-lateral and lateral corners are rounded. The posterior division of the lateral margin seems to be much shorter than the anterior division. The tergal angle (dma) is situated in between the anterior and middle thirds of the plate and is weakly marked. Overlap areas for ADL and MxL are normally developed as usually in Bothriolepis .

The dorsal lamina of the ADL is relatively narrow and long, with massive postnuchal ornamented corner. A new specimen of AVL collected from the type locality shows the anterior lateral corner of subcephalic division, which is situated in the middle between the median and lateral margins and developed into a short broad process (c.al, Fig. 21J ). The visceral surface of this specimen demonstrates the high transverse anterior crista (cit1) running antero-mesially and low and broad transverse thickening running more mesially.

REMARKS

Lahusen (1880) erected a new species B. panderi for the remains of bothriolepids collected by Pander & Trautschold from several localities at the Syas’ River. For the head-shield coming from Stolbovo locality and illustrated by Lahusen (1880: taf. 2, figs 2-4), Jaekel (1927) erected a new species B. traudscholdi . Gross (1932) proposed the head-shield MM 1/96 as a lectotype of B. panderi and mentioned B. traudscholdi as synonimous to B. panderi without any comments. Stensiö (1948) provided an extensive description of this species, based on the material described by Lahusen (1880), Trautschold (1880) and Gross (1933). In 1988, the author collected fragmentary AVL and ADL form the type locality, and revisited all available material from Syas’ River. In my opinion, specimens from the Stolbovo site belongs to separate species, namely B. traudscholdi (see below). Therefore the description of B. panderi provid- ed here differs greatly from those given by Gross (1933) and Stensiö (1948).

DISCUSSION

Bothriolepis panderi closely resembles B. cellulosa , but differs from it in features mentioned above in the description of B. cellulosa . This species also seems to be closely related to B. canadensis , but differs in 1) position of the infraorbital sensory groove; 2) much broader rostral plate; 3) higher dorsal wall of the trunkarmour; 4) more slender proximal segment of the pectoral fin.

The species B. panderi and B. taylori Miles, 1968 from Edenkillie Beds of Scotland ( Miles 1968) are clearly very close morphologically. They are similar in 1) the general proportions of the trunk-armour; 2) the shape of the dorsal wall; 3) the absence of the dorsal median ridge; 4) the shape of the anterolateral corner of AVL; 5) the shape and proportions of the Prm. B. taylori differs from B. panderi in its 1) larger size; 2) proportions of the AMD; 3) shape of the CD1. B. paradoxa (Agassiz, 1845) from the Scaat Craig Beds differs from B. panderi in the shape of Prm, shape and proportions of Nu, AMD and ADL, position of the tergal angle, the character of the ornamentation. (For the comparison of B. panderi with B. traudscholdi see the description of the latter).

Figures

FIG. 12. — Bothriolepis panderi Lahusen, 1880, lectotype, the complete head-shield and anterior part of the trunk armour MM 1/96. Right bank of Syas’ River near Montsevo village, Russia. Snetnaya Gora Beds. Scale bar: 10 mm.

FIG. 21. — Bothriolepis traudscholdi Jaekel, 1927; A-C, MxL; A, PIN 330/99; B, LDM 63/82; C, LDM 63/85; D-G, AVL; D, LDM 63/109 in ventral view; E, PIN 330/64 in ventral view; F, LDM 63/107 in ventral view; G, LDM 63/108 in visceral view; H, I, MV in ventral view; H, LDM 63/122; I, LDM 63/123. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation; J, Bothriolepis panderi Lahusen, 1880, anterior part of the AVL plate LDM 63/338 in visceral view. Right bank of Syas’ River near Montsevo village, Russia. Snetnaya Gora Beds. Abbreviations: AVL, anterior ventro-lateral plate; MV, median ventral plate; MxL, mixilateral plate; PMD, posterior median dorsal plate; c.al, antero-lateral corner of subcephalic division; cit1, crista transversalis interna anterior; cit2, transverse thickening on the visceral surface of AVL; cu, postero-ventral ornamented corner; d, dorsal corner; dlg2, posterior oblique dorsal sensory line groove; dlr, dorso-lateral ridge of trunk armour; f.ax, axillary foramen; lcg, main lateral line groove; oa.PMD, area overlapped by PMD; p.br, processus brachialis. Scale bar: 10 mm.

FIG. 2. — East Baltic Middle-Upper Devonian Regional Stages, vertebrate zones, and their correlation with the conodont dont and spore zones, modified after Blieck et al. (in press); Ivanov & Lukševičs 1996; Lukševičs 1995; Kleesment & Mark-Kurik 1997; Valiukevičius 1994. *Abava is Regional Substage being not yet accepted as a Regional Stage by the Baltic Devonian Subcommission. The black dots (•) indicate the conodont zones of the previous Standard Conodont Zonation identified in the succession of the Main Devonian Field (Žeiba & Valiukevičius 1972; Valiukevičius 1994; Kuzmin 1996). Miospore zones after Avkhimovitch et al. 1993. Abbreviations: Key to the miospore zones (Z.) and subzones (Subz.): BI, Acanthotriletes bucerus- Archaeozonotriletes variabilis insignis Subz.; CZ, Cyrtospora cristifer-Diaphanospora zadonica Z.; DE, Cristatisporites deliquescens- Verrucosisporites evlanensis Z.; EX, Geminospora extensa Z.; IM, Ancyrospora incisa-Geminospora micromanifesta Subz.; Im, Lagenoisporites immensus Z.; OG, Archaeoperisaccus ovalis-Verrucosisporites grumosus Z.; SD, Geminospora semilucensa- Perotrilites donensis Z.; SP, Spelaeotriletes papulosus Subz.; VV, Corbulispora vimineus-Geminospora vasjamica Z. B., Bothriolepis; P., Pycnosteus.

FIG. 3. — Stratigraphic charts of the Middle and Upper Devonian of the East Baltic and NW Russia, after Kleesment & Mark-Kurik 1997; Narbutas 1994; Rzhonsnitskaya & Kulikova 1990; Lukševičs, Mūrnieks & Savvaitova 1999; Gailīte et al. 2000 (modified). The names of the stratigraphical units of the north-western Russia here and below follows Rzhonsnitskaya & Kulikova 1990. Abbreviations: B-s, Beds; Mb, Member.

FIG. 4. — Bothriolepis prima Gross, 1942; A, incomplete head-shield LGI 5-2202; B, incomplete head-shield LGI 5-2203; C-E, restored trunk armour, based on the right ADL LGI 5-2699, MxL LGI 5-2700, AVL LGI 5-2701, right PVL LGI 5-2702 and left PVL LGI 5-2703 in lateral, dorsal and ventral views (produced by V. Talimaa). Daugava River near Pastamuiža, Latvia. Amata Formation. Abbreviations: ADL, anterior dorso-lateral plate; AVL, anterior ventro-lateral plate; MxL, mixilateral plate; PVL, posterior ventro-lateral plate. Scale bar: 10 mm.