Bothriolepis tremdscholdi, Lukševičs, 2001

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 : 521-534

Bothriolepis traudscholdi Jaekel, 1927 ( Figs 13-22 )

Bothriolepis panderi Lahusen, 1880: 137 , taf. 2, figs 2-4. — Trautschold 1880: 172 (fig.). — Gross 1932: 25 (p.p.); 1933: 39, 40, taf. 4, fig. 6; abb. 21; 1941: abb. 10B, C, 11G, H, 26H-K, 27D, E. — Stensiö 1948: 424; text-fig. 229A, 231 [non textfig. 230]. — Watson 1961: text-fig. 1. — Obruchev 1964: pl. 6, fig. 6.

Bothriolepis tremdscholdi – Jaekel 1927: 869, abb. 21.

Bothriolepis traudscholdi Jaekel, 1927: 932 , abb. 60. — Gross 1932: 25; 1933: 40 (nomen negatum).

TYPE SPECIMEN. — Jaekel (1927) proposed a new species of Bothriolepis for a head-shield collected by Trautschold (1880, shown also by Gross in 1933) at Syas’ River not far from Stolbovo village ( Russia), said to be held in the Museum of Breslau (now Wroclaw in Poland). Part of the Trautschold collection is held in this museum, but the specimen shown by Jaekel cannot be located (pers. comm. A. Ivanov). Therefore, I propose here the head-shield PIN 330/33, collected by J. Eglons in 1937 at the type locality and illustrated by Obruchev (1964: pl. 6, fig. 6), as a neotype of Bothriolepis traudscholdi .

MATERIAL EXAMINED. — PIN 330/39, 41-75, 77-98, 100-107, 110-128, 29/1, 2, articulated head-shields and disarticulated plates of the skull roof and trunk armour; PIN 2917/41-46, articulated head-shields and anterior divisions of the trunk armour; LDM 63/1-33, 35-51, 53-230, 241-396, IEC LP 12/1-5, disarticulated plates of the skull roof and trunk armour; IEC LP 12/6, articulated plates of the dorsal trunk armour; NHM P.34465, sandstone block with 20 bones, including articulated head-shields; RSM 1902.72.4, AMD, 1902.72.6, PMD. Disarticulated plates of the headshield LDM 71/18, Prm, 71/51, Nu, 71/52, La; disarticulated plates of the trunk armour LDM 71/2, 34, 36, 38, 39, 42, 45, 47, 50, 87, 89-92, 97, 161 and plates of the pectoral fin LDM 71/54-57, 62, 101, 125, 131, 132 are tentatively referred to this species.

LOCALITIES AND HORIZON. — The type locality is an outcrop of dark red-coloured sandstone with thin layers of clayey siltstone, multicolored marl and clay, on the right bank of the Syas’ River near Stolbovo village, Russia. Other material comes from the outcrops at Syas’ River near Yukhora village, not far from Stolbovo, and exposure of the dolomites at the left bank of the Gauja River not far from Vidaga village, Latvia. All Russian material comes from the Frasnian Dubnik Formation. The Latvian material comes from the Altovo Member of the Daugava Formation. A possible new form of Bothriolepis from the Matusevich Formation of Severnaya Zemlya seems to be closely related to Bothriolepis traudscholdi from the Main Devonian Field (Lukševičs 1999).

DIAGNOSIS. — Rather large Bothriolepis with a medi- an dorsal armour length of at least 140 mm. Headshield of moderate width, B/L index 133, with strongly convex anterior margin shorter than posterior margin. Orbital fenestra long. Preorbital recess of simple type. Nu moderately broad with B/L index of about 81; it is broadest across the postero-lateral corners. AMD moderately broad, B/L index about 94. The anterior margin 1.9 time shorter than the maximum width of the plate. Postnuchal notch pronounced, with very strong anterolateral corners. Median dorsal ridge weakly developed and practically absent in large individuals. PMD is relatively broad with B/L index about 104. Postnuchal ornamented corner of the ADL is sharp, long and narrow. Axillary fenestra longer than high. Proximal segment of the pectoral fin is slender, about 4.4 times as long as broad; it bears separate relatively small lateral and mesial spines, which are almost similar to the tubercles, composing the ornamentation. The point contact between MM1 and CV2 of pectoral fin results in separation of CV1 from MM2. The ornamentation is fine-meshed in very small individuals, typically tubercular in medium-sized individuals and has mixed character in large individuals, consisting of tubercles and anastomosing ridges on the skull roof and plates of the trunk armour. DESCRIPTION

This species is well-represented at the type locality by many disarticulated plates, as well as some articulated skulls and trunk shields, which are usually well-preserved. Almost all specimens from the Vidaga site are incomplete and usually deformed, in many cases preserved only as an impressions. Most are from small or well-grown individuals of moderate size, but there are also some quite large specimens.

The length of the head shield reaches about 75 mm, the dorsal length of the trunk armour is estimated at least about 140 mm. The head shield ( Figs 13A, B ; 14 A-C; 15A-D) has B/L index is of 130-140 (of average 133, n = 4). It is strongly vaulted both rostrocaudally and transversely in small individuals, but is flat in the well-grown individuals. There are well-defined anterolateral corners (alc) and a deep prelateral notch (nprl). The obtected nuchal area (nm) is of moderate width, broadest on the Nu, and usually with well-defined lateral and median processes. The orbital fenestra is moderately large, long, with a B/L index about 150-167, 156 on the average.

The visceral skull surface ( Figs 13B ; 14B ; 15D ) shows the broad otico-occipital depression (ood), which is well-defined by the paramarginal cristae (cr.pm). The antero-lateral corner of otico-occipital depression (pr.po) is narrow in its base, postero-lateral corner extends laterally not over the middle of the Pn’s posterior margin. The transverse lateral groove is moderately broad and clearly defined. The small, deep lateral pit (p) is situated closer to a prelateral notch than to the orbital edge of La. The attachment areas for the Prl and Sm on the La differs slightly from that of B. canadensis (e.g., Stensiö 1948: fig. 12) in that the overlap area for Prl is only slightly visible from the ventral side, as in Bothriolepis sp. from Gogo or B. portalensis (see Young 1988: fig 66B, D). The median occipital crista (cr.o) is slightly defined, often it consists of several radially arranged small ridges. The transverse nuchal crista is prominent, with the median part extending anteriorly. The median ridge (mr) sharing the moderately deep paired pits (g) of Pp is low.

The Prm is relatively broad, B/L index 90-110, 99 on the average. Usually it is broadest somewhat posteriorly the infraorbital sensory groove. The rostral angle (ac) usually is absent. The shape of the rostral margin is variable, often it is convex. The orbital margin is gently convex and well shorter than the rostral margin. The nasal notch (pnn) on the orbital margin is not well-defined. The anterior section of the supraorbital sensory line (soc) usually is clearly defined.

The La is moderately broad with L/B index of 130-143, 134 on the average. The rostral margin is almost straight, the antero-median and antero-lateral corners are well-defined. The infraorbital sensory groove crosses the plate in its anterior part not far from the orbital and lateral margins. The central sensory line groove (csl) usually is finished at the level of the anteri- or margin of the orbital fenestra.

The Pp is broad both in small and moderatesized individuals, L/B index varies from 57 to 71. The anterior margin remains convex with increasing size of individuals.

The Nu is moderately broad with a L/B index 71-90, 81 on the average. The anterior division of the lateral margin usually is almost straight and well shorter than the posterior division. The shape of the posterior margin is variable, sometimes it is strongly concave, often bears the posterior process (mppr). The central sensory line groove is clearly distinct. Usually there are short supraoccipital grooves (socc), which terminate little in front of the obtected nuchal area at the external openings for the endolymphatic ducts (d.end). Postorbital crista (cr.pto) on the visceral surface is moderately high.

The Pn is moderately long, L/B index 71-103, 88 on the average. Sometimes (in PIN 330/115) it bears short middle pit-line (mp). The lateral division of the Pn is moderately broad and is composing 45-68% of the general breadth of a plate.

The Pmg is relatively broad with lateral margins longer than the median margins.

The submarginal (extralateral) plate ( Figs 14 E-J; 15H-J) is comparatively long with L/B index about 220-270. The dorsal margin has a prominent anterodorsal process (ad1) and a narrow posterior attachment area for the skull. The posterior margin is almost straight, the ventral margin is weakly to strongly concave. A wellmarked lateral notch is rather deep separating the plate into a short thick anterior division and more thin posterior division. The specimen PIN 330/116 ( Figs 14G ; 15H ) shows a groove (gr.sc) running along the dorsal margin of the ornamented part of the plate in its posterior division, which is similar to that of Bothriolepis obrutschewi (pers. obs.) and B. macphersoni and has the character of a sensory groove.

The trunk armour in individuals of moderate size is known from a large amount of disarticulated plates and several anterior parts of articulated armours, sometimes with articulated pectoral fins, of small individuals.

The trunk-armour in individuals of small size as it is remained in specimens PIN 2917/41-46 is moderately broad, B/L index 86. It is relatively low with moderately high dorsal wall. The maximum length of the dorsal wall, probably, is about 140 mm. The median dorsal ridge is welldefined in small individuals, weakly developed in medium-sized individuals and represented only in its posterior part in large individuals. The dorso-lateral and ventro-lateral ridges are well-marked in small individuals and are round- ed in large individuals.

The AMD is moderately broad, B/L index varying from 84 to 105, 94 on the average. The anterior margin is generally convex, sometimes somewhat wavelike in shape, relatively long. The anterior margin is usually 1.1 time longer than the posterior margin. The antero-lateral and lateral corners are well-defined. The posterior division of the lateral margin is 1.5-1.9 time shorter than the anterior division. The tergal angle (dma) is situated slightly posteriorly the anterior third of the plate. The median dorsal ridge (dmr) is well-developed on the small 17- 23 mm long plates; it is slightly defined behind the tergal angle on the plates of moderate size with the length 24-25 mm. More large plates with the length over 26 mm have no median dorsal ridge. The postnuchal notch (npn) is broad and shallow, the postlevator process (pr.pl) is well-defined. The anterior oblique dorsal sensory line groove (dlg1) is gently defined only in smallest specimen LDM 63/17 which is 17 mm long. The posterior oblique dorsal sensory line groove (dlg2) is clearly defined also on the plates of very large individuals. Specimen LDM 63/18 ( Fig. 17A ) shows the posterior oblique dorsal sensory line groove developed only on the left lamina of the plate. Overlap areas for ADL and MxL mostly are normally developed as usually in Bothriolepis , but in LDM 63/30 ( Fig. 17G ), 63/8, and 71/34 ( Fig. 17H ) sutural connection of AMD with MxL is of Remigolepis type. The antero-lateral margins in LDM 63/37 ( Fig. 16G ) and PIN 330/53 ( Fig. 16H ) are partly overlapped by ADL, in 63/14 such overlapped area is developed on the right side (the left side is broken).

The visceral surface of the AMD ( Figs 16B, C ; 17E ) shows a moderately broad levator fossa (f.retr), which is limited by the low postlevator thickenings (alr). The supranuchal area (sna) is clearly seen, but relatively narrow. The median ventral ridge (mvr) and the median ventral groove (grm) are developed similar as in other Bothriolepis .

The PMD is variable, usually broad, sometimes very broad (in LDM 63/65), or relatively narrow (in PIN 330/47 and PIN 330/48), B/L index varies from 91 to 112, 104 on the average. Whether the differences in proportions of the plate reflects sexual dimorphism or even presence of two species within the material, is very hard to say, because in other respects narrow and broad plates does not differ. The PMD is anteriorly almost flat and arched in the posterior part. The dorsal median ridge is well-marked along the whole plates in small individuals and in the posterior half of PMD in medium-sized and large individuals. The anterior margin is 1.7 to 2.2 times as long as the total width of the plate, it is variable in its shape, usually without distinct anterior corner. The posterior margin usually has rounded, sometimes concave or pointed posterior median corner. The lateral margins of the plate generally overlapping the MxL, but in LDM 63/58 there are narrow areas along the lateral process of the PMD overlapped by the MxL ( Fig. 19C ).

On the visceral surface ( Figs 18B ; 19D ), the ventral median groove (grm) is clearly shown also in small specimens, the ventral median ridge (mvr) is low with shallow posterior ventral pit, which is situated in posterior half of the plate. Posterior marginal area (pma) is relatively short. The ADL ( Figs 18 F-K; 20) has relatively elongated dorsal lamina. The posterior margin of the lateral lamina is approximately equal in breadth to the posterior margin of the dorsal lamina. The lateral lamina is about three times as long as it is deep. The dorso-lateral ridge is well-marked in the posterior part of the plate. The postnuchal ornamented corner (pnoa) resembles that of B. ciecere ; in large specimens it is more broad. Notch behind it is poorly formed. The dorsal margin of the plate bears an overlap area for the AMD usually along the whole of its length, but in specimens PIN 330/86 ( Figs 18G ; 20A ) and 330/98 ( Figs 18J ; 20B ) the ADL overlaps the AMD by its posterior half. Processus obstans is well-developed, with high articulation lamina. The articular fossa for the exoskeletal cervical joint (f.art) is clearly demarcated by well-developed supra- and infra-articular cristae (crs, cri) ( Figs 18K ; 20C ).

The MxL ( Figs 18E ; 21 A-C) has a comparatively low lateral lamina which is more than 3 times as long as it is deep, and a relatively broad dorsal lamina about 1.6-1.7 time as long as it is broad. The anterior margin concave or wavy. Dorsal and lateral laminae meet at an angle of about 113°. Dorsolateral ridge is well-marked, in large specimens it is rounded. Overlap area for the AMD in specimen PIN 330/94 ( Fig. 18E ) is restricted to half the length of the antero-dorsal margin, as in Remigolepis .

The AVL ( Fig. 21 D-G) is comparatively broad, the ventral lamina is 1.5-1.8 time as long as it is broad. The subcephalic division comprises 20- 25% of the total length of a ventral lamina. The ventral lamina 2.1-3 times as broad as the lateral lamina high. The lateral lamina is low, 3- 3.8 times as long as it is high. The ventro-lateral ridge is well-defined, sometimes rounded off. The axillary foramen (f.ax) is rather large and elongated. The visceral surface of the AVL shows the high transverse anterior crista (cit1) running antero-mesially very close to the broad transverse thickening (cit2).

The PVL ( Fig. 22A, B ) is of moderate breadth, the ventral lamina is 2-2.5 times as long as it is broad. The subanal division is relatively broad and long, it occupies about 30-36% of the total PVL length. The lateral lamina is moderately high, 1.8-2 times long as it is high. The ventral lamina 1.2-1.3 time as broad as the lateral lamina high. The ventro-lateral ridge (vlr) is welldefined.

The pectoral fin is represented by many disarticulated bones, and four specimens showing articulated plates of the proximal segment ( Figs 18L ; 22 C-F). The comparatively slender proximal segment bears separate relatively small lateral and dorsally directed mesial spines; the latter are usually similar to the tubercles composing the ornamentation. The proximal segment is 4.1- 4.6 times as long as it is broad. The CD1 is of moderate size with L/B index varying from 2.6 to 3.1 (2.8 on the average, n = 4). The CV1 is relatively more elongated and have the L/B index about 2.8-3.6 (3.2 on the average). The ML2 is 4.8-5.7 (5.2 on the average) times as long as it is broad.

The ornamentation is fine-meshed reticulate in very small individuals, e.g. 18.9 mm long PMD plate LDM 63/270, and typically tubercular in general in medium-sized and quite large individuals, becoming coarser and sparser. It consists of coarse tubercles and anastomosing ridges of fused tubercles on the head shield. The tubercles cover usually almost all the surface of the Prm, Pm, partly La, Pn and Pp. The ornament on the Sm consists of ridges and tubercles. The ornament on the plates of the trunk armour is typically tubercular in general, but retains its very variable character. Some plates have all possible patterns of the ornament on their surface, especially in large specimens. The ornamentation of the pectoral appendage is also variable. It is reticulate in general, on the CD1 and dorsal lamina of the ML2 the network ridges bear tubercles in the points of anastomoses only along the lateral margin, more well-developed in proximal part. The ornament on the ventral side of the pectoral appendage is reticular in general.

REMARKS

Bothriolepis traudscholdi was illustrated by Jaekel (1927) as a new species from Syas’ River which differs from B. panderi , but he did not provide its description. This species was named as “ Bothriolepis tremdscholdi n. sp. ” in explanation to abb. 21 and “ B. traudscholdi Jkl. ” in abb. 60 of Jaekel’s (1927) paper; both were regarded to be misprintings by Gross (1933) and he incorrectly changed the original spelling into B. trautscholdi in a list of synonyms to B. panderi . However, in the catalogue of antiarchs, Gross (1932) have used the name B. traudscholdi , but did not clearly define this action. Therefore, acting as a first reviser, I propose here to choose the name Bothriolepis traudscholdi as a valid name for this taxon. Gross (1933) mentioned B. traudscholdi as a synonymous to B. panderi , but without any further comments. Stensiö (1948) agreed with Gross (1933) and provided description of B. panderi including material, which I suppose to be attributable to B. traudscholdi . The description of B. traudscholdi here is based on extensive material from the type locality, gathered by J. Eglons & D. Obruchev in 1937, L. Lyarskaja in 1974, and author together with A. Ivanov in 1988. This material was never described in details, being only mentioned as belonging to B. panderi (e.g., Obruchev 1964). Specimens from Vidaga site at Gauja River were collected by Lyarskaja in 1978 and the author together with Lyarskaja in 1983.

DISCUSSION

Bothriolepis traudscholdi resembles B. panderi by several features: 1) the general shape of the head-shield; 2) proportions of the Pn and Pmg; 3) general proportions of the trunk armour; 4) weak development of the dorsal median ridge; 5) position of the tergal angle; 6) proportions of the ADL; 7) proportions of the slender pectoral fin. Nevertheless, B. traudscholdi differs considerably from B. panderi in its 1) comparatively narrower head-shield; 2) more vaulted anterior part of the head-shield; 3) larger and longer orbital fenestra; 4) shape and proportions of the Prm and Nu; 5) more anterior extent of the central sensory line groove; 6) more broad AMD; 7) shorter anterior margin of the AMD; 8) shape of the postnuchal ornamented corner of the ADL; 9) longer subcephalic division of the AVL.

B. traudscholdi differs well from B. obrutschewi in its strongly larger size, shape and proportions of the Prm and Nu, relative length of the anteri- or margin of the AMD, shape and proportions of the PMD, ADL and MxL, as well as more elongated pectoral fin. B. traudscholdi can be distinguished readily from B. cellulosa by larger size, shape and proportions of the La and Nu, relative length of the anterior margin of the AMD, shape and proportions of the AMD, PMD and MxL, more elongated pectoral fin and tubercular rather than reticular ornamentation.

Figures

FIG. 13. — Bothriolepis traudscholdi Jaekel, 1927; A, B, head-shield PIN 330/113 in dorsal and visceral views; C, Prm PIN 330/126 in dorsal view; D, Prm PIN 330/127 in dorsal view; E, La PIN 330/124 in dorsal view; F, Pn LDM 63/138 in dorsal view; G, Nu LDM 63/149 in dorsal view; H, I, Nu and Pp PIN 330/42 in dorsal and visceral views; J, Nu LDM 63/156 in visceral view. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: La, lateral plate; Nu, nuchal plate; Pn, paranuchal plate; Pp, postpineal plate; Prm, premedian plate. Scale bar: 10 mm.

FIG. 14. — Bothriolepis traudscholdi Jaekel, 1927; A, B, head-shield PIN 330/117 in dorsal and visceral views; C, head-shield PIN 330/125 in dorsal view; D, La PIN 330/115 in visceral view; E, La PIN 330/112 in dorsal view; F, Prm PIN 330/46 in dorsal view; G, H, Sm PIN 330/116 in lateral and visceral views; I, J, Sm PIN 330/114 in lateral and dorsal view. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: La, lateral plate; Prm, premedian plate; Sm, submarginal plate. Scale bar: 10 mm.

FIG. 15. — Bothriolepis traudscholdi Jaekel, 1927; A, head-shield PIN 330/113 in dorsal view; B, head-shield, anterior part of AMD, left ADL,AVL, CD1 and CV1 PIN 2917/45 in lateral view; C, head-shield, anterior part of AMD, both ADL, right AVL and proximal segment of the pectoral fin PIN 2917/43 in dorsal view; D, head-shield PIN 330/117 in visceral view; E, Prm PIN 330/118; F, Nu LDM 63/149; G, La LDM 63/131; H-J, submarginal plates; H, PIN 330/116 in lateral view; I, J, PIN 330/114 in lateral and ventral views. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: ADL, anterior dorso-lateral plate; AMD, anterior median dorsal plate; AVL, anterior ventro-lateral plate; CD1, dorsal central plate 1; CV1, ventral central plate 1; La, lateral plate; ML2, lateral marginal plate 2; Nu, nuchal plate; Pmg, postmarginal plate; Pn, paranuchal plate; Pp, postpineal plate; Prm, premedian plate; Sm, submarginal plate; ad1, anterior articular process; ad2, posterior articular process; cir, semicircular pit-line groove; cr.o, median occipital crista of head-shield; cr.pm, paramarginal crista of head-shield; cr.tv, transverse nuchal crista of head-shield; csl, central sensory line groove; fe.orb, orbital fenestra; g, paired pits on Pp; gr.sc, groove, possible for sensory canal; ifc1, principal section of infraorbital sensory line; ifc2, branch of infraorbital sensory line diverging on La; lpr, lateral process of head-shield; mp, middle pit-line groove; nm, obtected nuchal area; nprl, prelateral notch; ood, otico-occipital depression; p, lateral pit; prh, preorbital recess; pr.po, antero-lateral corner of otico-occipital depression; soc, anterior section of the supraorbital sensory line. Scale bars: 10 mm.

FIG. 16. — Bothriolepis traudscholdi Jaekel, 1927, AMD; A, D-H, dorsal views; A, LDM 63/41; D, PIN 330/56; E, PIN 330/55; F, PIN 330/52; G, LDM 63/37; H, PIN 330/53; B, C, visceral views; B, LDM 63/44; C, PIN 330/57. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviation: AMD, anterior median dorsal plate. Scale bar: 10 mm.

FIG. 17. — Bothriolepis traudscholdi Jaekel, 1937, AMD; A-D, F-H, dorsal views; A, LDM 63/18; B, LDM 63/24; C, LDM 63/7; D, PIN 330/52; F, LDM 63/67; G, LDM 63/30; H, LDM 71/34; E, visceral view, LDM 63/13. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Left bank of Gauja River near Vidaga village, Latvia. Kranciems Member of the Daugava Formation. Abbreviations: AMD, anterior median dorsal plate; MxL, mixilateral plate; PMD, posterior median dorsal plate; alr, postlevator thickening; dlg2, posterior oblique dorsal sensory line groove; dma, tergal angle; dmr, dorsal median ridge; f.retr, levator fossa; grm, ventral median groove; mvr, median ventral ridge; npn, postnuchal notch; oa.MxL, area overlapped by MxL; oa.PMD, area overlapped by PMD; pr.pl, external postlevator process; pt1, anterior ventral pit. Scale bar: 10 mm.

FIG. 18. — Bothriolepis traudscholdi Jaekel, 1927; A, PMD PIN 330/47 in dorsal view; B, PMD PIN 330/58 in visceral view; C, PMD PIN 330/48 in dorsal view; D, PMD LDM 63/58 in dorsal view; E, MxL PIN 330/94 in dorsal view; F, ADL LDM 63/98 in dorsal view; G, ADL PIN 330/86 in dorsal view; H, I, ADL PIN 330/87 in dorsal and lateral views; J, K, ADL PIN 330/98 in dorsal and anterior views; L, proximal segment of the pectoral fin PIN 330/68 in ventral view. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: ADL, anterior dorso-lateral plate; MxL, mixilateral plate; PMD, posterior median dorsal plate. Scale bar: 10 mm.

FIG. 19. — Bothriolepis traudscholdi Jaekel, 1927, PMD; A-C, dorsal views; A, LDM 63/76; B, LDM 63/71; C, LDM 63/58; D, visceral view, PIN 330/50. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: MxL, mixilateral plate; PMD, posterior median dorsal plate; cr.tp, crista transversalis interna posterior; dmr, dorsal median ridge; oa.MxL, area overlapped by MxL; pma, posterior marginal area of PMD; pt2, posterior ventral pit. Scale bars: 10 mm.

FIG. 20. — Bothriolepis traudscholdi Jaekel, 1927, ADL; A, PIN 330/86 in dorsal view; B, C, PIN 330/98 in dorsal and anterior views; D, E, PIN 330/87 in dorsal and lateral views; F, LDM 71/45 in dorsal view, somewhat flattened; A-E, right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation; F, left bank of Gauja River near Vidaga village, Latvia.Kranciems Member of the Daugava Formation. Abbreviation: ADL, anterior dorso-lateral plate. 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. 22. — Bothriolepis traudscholdi Jaekel, 1927; A, B, PVL; A, LDM 63/114 in ventral view; B, LDM 63/113 in visceral view; C, proximal segment of the pectoral fin PIN 330/68 in ventral view; D, part of the proximal segment of the pectoral fin LDM 63/132 in dorsal view; E, part of the proximal segment of the pectoral fin LDM 63/139 in dorsal view; F, CV1 LDM 63/158 in ventral view. Right bank of Syas’ River near Stolbovo village, Russia. Dubnik Formation. Abbreviations: AVL, anterior ventro-lateral plate; CD1, dorsal central plate 1; CD2, dorsal central plate 2; CV1, ventral central plate 1; CV2, ventral central plate 2; ML2, lateral marginal plate 2; MM2, mesial marginal plate 2; MV, median ventral plate; MxL, mixilateral plate; PVL, posterior ventro lateral plate; cf.MV, area overlapping MV; cf.MxL, area overlapping MxL; cf.PVL, area overlapping PVL; cm1, anteromesial corner of ventral lamina of PVL; cm2, middle corner of ventral lamina of PVL; dc, dorsal corner of lateral lamina of PVL; oa.AVL, area overlapped by AVL; vlr, ventrolateral ridge. Scale bar: 10 mm.