Bothriolepis heckeri, 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 : 569-577

Bothriolepis jani Lukševičs, 1986

( Figs 55-61 )

Bothriolepis jani Lukševičs, 1986: 131 , pl. 1, fig. 8.

HOLOTYPE. — Right MxL LDM 100 /88.

MATERIAL EXAMINED. — LDM 100/526, articulated head-shield, LDM 100/66-108, 100/119-122, 100/137, 100/148, 100/374-377, 100/431-434, disarticulated plates of the trunk armour; 100/109-118, 100/123- 136, 100/370, 100/371, 100/378, 100/435-440, plates of the pectoral appendage; 100/144, 100/427, 2 Prm; 100/369, 100/428, 2 La; 100/429, LGI 5/2028, 2 Pp; LDM 100/138-143, 100/372, 100/430, 8 Nu.

LOCALITIES AND HORIZON. — The type locality is an exposure of white and pink sandstone containing abundant fish bones, dolomite marl and marl at the right bank of Skujaine River down Klūnas village (number 8 in Fig. 1 ); the Famennian Tērvete Formation. Other material comes from an outcrop of red and pink sandstone at the right bank of Svēte River near Ķurbes hamlet (number 9 in Fig. 1 ); the Mūri Formation.

DIAGNOSIS. — Small Bothriolepis with a median dorsal armour length reaching about 65 mm. B/L index of trunk-armour about 90. Prm broad, posterior margin is slightly shorter than almost straight anterior margin. Nu strongly arched, L/B index of 59; AMD strongly arched, B/L index 97. Anterior margin of AMD is broad, posterior margin of AMD and anteri- or margin of PMD are narrow. Median dorsal ridge strongly developed. Lateral line sensory groove terminates on posterior margin of the MxL. Proximal segment of pectoral appendage three times as long as broad, with prominent lateral and mesial spines. Ornamentation reticulate in small individuals and typically tuberculate in well-grown individuals, consisting of numerous closely irregularly set round- ed tubercles.

DESCRIPTION

This species is represented mainly by disarticulated plates, single articulated, but slightly deformed head-shield and a single articulated proximal segment of the pectoral fin. The headshield ( Figs 55A ; 56A ) has an estimated B/L index of about 127, and is strongly vaulted both rostrocaudally and transversely. The rostral margin is convex, shorter than the posterior margin, which is straight and bears a welldefined posterior median process. The anterolateral corners and shallow prelateral notch are well-defined. The obtected nuchal area is long, extending onto the Pn, it is broadest on the Nu. The orbital fenestra is relatively large (B/L index about 176). The preorbital recess is of pentagonal type.

The Prm is broad, B/L index of about 116, arched, with an almost straight rostral margin, as in LDM 100/144, which is an anterior division of the Prm ( Fig. 55B ). LDM 100/427 is a more complete smaller Prm ( Fig. 56B ) which is more arched, and broadest at the rostral margin. The rostral margin more than twice longer than the concave orbital margin. The infraorbital sensory groove crosses the plate far from the rostral margin, unlikely that in B. ornata . The anterior section of the supraorbital sensory line is not recognized.

The La ( Fig. 55D ) is broad with L/B index of about 136-137 (n = 2). The rostral margin is of moderate breadth and almost straight. The infraorbital sensory groove crosses the plate almost in its middle part far from the orbital and lateral margins. The central sensory line groove (csl) extends slightly past the middle of the orbital fenestra. The antero-lateral corner of the otico-occipital depression on the visceral surface is relatively narrow and extends forward at the level of the middle of orbital fenestra length. The preorbital recess is not clearly seen, but the outlines on the visceral surface of specimen LDM 100/369 allows to suggest that it could be of trifid type.

The very broad Pp (LDM 100/429: Figs 55 ; 56C , and LGI 5/2028) has a strongly convex anterior margin. A narrow median ridge (mr) separates the deep paired pits (g) on the visceral surface of the plate. Both specimen clearly differ from the Pp of similar size (LDM 100/373) of B. ornata which comes from the same locality, by their tubercular ornament and broader general proportions.

The Nu ( Figs 55 E-G; 56D-G) is strongly arched with an angle between right and left halves about 103-125°. It is relatively short and broad (L/B index 57-63, 59 on the average). The anterior division of the lateral margin is much short- er than the posterior division. The obtected nuchal area (nm) is relatively long, it extends on the Pn. In specimens LDM 100/140 and 100/372 ( Fig. 56F ), there are supraoccipital grooves (socc) which terminate little in front of the obtected nuchal area at the large external openings for the endolymphatic ducts (d.end). Specimens LDM 100/141, 100/142, 100/430 ( Figs 55 E-G; 56D-E), and 100/527 show welldefined middle pit-line grooves (mp), which are not connected with endolymphatic opening and extend to the lateral margin of the plate. The median occipital crista (cr.o) and the transverse nuchal crista are well-defined. The postorbital crista (cr.pto) on the visceral surface is weakly developed, it can be recognised only in LDM 100/372 ( Fig. 56G ) as a sharp transversely directed crest binding the orbital facets posteriorly.

The dorsal trunk armour is relatively broad, B/L index 90. It is relatively low, with a lateral wall less than three times as long as high, with high dorsal wall. Length of the dorsal wall reaches 65 mm. Right and left dorsal laminae enclose an angle about 115°. The dorsal and lateral walls enclose an angle 120° in the MxL and about 125-130° in the ADL. The median dorsal ridge is well-defined. The dorso-lateral and ventro-lateral ridges are wellmarked in a posterior part of the trunk armour.

The AMD ( Figs 55 J-L; 57) with B/L index about 91-110, 97 on the average, in large individuals it is broader than long, as in B. maxima . The plate is strongly arched, with right and left laminae forming an angle at the level of lateral corners of about 115° on the average. The anterior margin may be weakly concave or fairly straight. It is broad and 1.2-2 times as long as a narrow posterior margin. The tergal angle (dma) is well-marked. The median dorsal ridge is strongly developed and in small individuals represented by the low crest. Overlap areas for MxL are developed as in Remigolepis ( Stensiö 1931) . The visceral surface of the AMD shows a broad levator fossa (f.retr), which is limited by the low postlevator thickenings (alr) and strongly developed postlevator crest (cr.pl) with pronounced kink. The anterior edge of the crest do not reach a distinct, but narrow supranuchal area.

The PMD ( Figs 55 H-I; 58A-D) is arched, moderately broad, B/L index about 87-104. The width of the anterior margin comprises about 54% of total breadth. The median dorsal ridge is well-developed.

The ADL ( Figs 55M, N ; 58E, F ) is moderately broad. The dorsal lamina is relatively narrow and long, and its breadth a little exceeds height of the lateral lamina. Dorsal and lateral laminae of the plate enclosing an angle of 125-130°. The dorso-lateral ridge (dlr) is well-defined in the posterior part of the plate, it is rounded in the anterior third of the ADL.

The dorsal lamina of the MxL ( Figs 55 O-R; 59A-D) is less than twice as long as it is broad. The dorsal lamina is 1.7 time as broad as the lateral lamina is high. Dorsal and lateral laminae enclosing an angle about 120°. The lateral lamina is relatively high, 2.4 times as long as it is broad. The dorso-lateral ridge is well-defined. The lateral line sensory groove terminates on the posterior margin of the plate above the postero-ventral ornamented corner (cu), posterior part of the sensory groove is traced not along the suture between the MxL and PMD as usually in Bothriolepis , but on the outer surface of the MxL.

The AVL ( Figs 59E, F ; 60A, B ) is of moderate breadth, the ventral lamina is about 2.5 times as long as it is broad. The ventral lamina 2.3 times as broad as the lateral lamina high in LDM 100/433 ( Fig. 59E ). Ventro-lateral ridge is welldefined. The axillary foramen (f.ax) is rather large and slightly elongated in shape. The visceral surface of the AVL shows the high transverse anterior crista (cit1) running mesially subparallel to the low and broad transverse thickening (cit2), just like as in B. ciecere , B. macphersoni Young, 1888 and B. karawaka Young, 1888 .

There are two complete PVL LDM 100/434 ( Figs 60C ; 61A ) and LDM 100/375. In LDM 100/434, its ventral lamina is 2.1 times as long as it is broad. The subanal division is relatively broad, it occupies only 17.7% of the total PVL length. The lateral lamina is 2.6 times as long as it is high, the ventral lamina is 1.5 time as broad as the lateral lamina high. The ventral and lateral laminae encloses the angle about 112°. The ventro-lateral ridge (vlr) is welldeveloped.

The MV is unknown, but the shape of the AVL and PVL suggests the small size of the MV.

The pectoral fin is represented mostly by disarticulated bones, and specimen LDM 100/435 ( Figs 60G ; 61B ) showing articulated plates of the proximal segment without the most proximal part. The proximal segment bears large prominent lateral and mesial spines. It is relatively broad, about three times as long as it is broad. The CD1 is of moderate size with L/B index varying from 2.8 to 3. The CV1 is slightly more elongated than the CD1 (L/B 3.3). The ML2 is 4.4-5.5 (4.9 on the average) as long as it is broad.

The ornamentation is reticulate in small individuals and typically tuberculate in well-grown individuals. It consists of numerous closely and usually irregularly set tubercles, which usually are rounded. They are tall on the Prm and short on most of the other plates. Along the obtected nuchal area on the Nu and posterior margin of the lateral lamina of the PVL tubercles may fuse into ridges. More regular setting of tubercles is recognized on the proximal segment of the pectoral fin.

REMARKS

The holotype and most of the material (collection LDM 100) came from the Skujaine locality, collected by the author in 1984, 1989 and 1998. Some studied specimens (e.g., LGI 5/2028) were found by Karatajūte-Talimaa in the same locality. Other material (e.g., LDM 100/524) was collected by the author in the Ķurbes locality.

DISCUSSION

B. jani differs from most of other Bothriolepis by its tuberculate ornament, which is similar to that of Grossilepis tuberculata and G. spinosa . B. jani differs from G. tuberculata in its 1) shape and proportions of the PMD, MxL and PVL; 2) sutural connections of the AMD and MxL; 3) shape of the postnuchal ornamented corner of the ADL; 4) larger axillary foramen; 5) proportions of pectoral fin bones.

Most of the described specimens come from the locality at Skujaine River downstream Klūnas village, associated with B. ornata . A comparison of B. jani with B. ornata is given at the end of the description of B. ornata .

B. jani can be distinguished readily from the other Famennian Bothriolepis species of similar size ( B. cristata , B. hydrophila [ Miles 1968] and small specimens of B. ciecere ) by its tuberculate ornament. B. jani differs well from B. nielseni Stensiö, 1948 in absence of the crest on the dorso-lateral ridge. Bothriolepis , described by Gross (1942) from locality at Svēte River, resembles B. jani by its tubercular ornament but differs in absence of a prominent ventro-lateral ridge on the PVL. The species B. jani and B. lohesti Leriche, 1931 (see Stensiö 1948) from Belgium are similar in 1) the shape and proportions of the AMD; 2) sutural connections between AMD and MxL. Unfortunately, B. lohesti is only represented by a few remains of AMD, ADL and pieces of the pectoral fin bones. It differs in that 1) the AMD is less arched; 2) ornament consists of tubercles and nodose ridges, but it seems likely that B. jani and B. lohesti may be phylogenetically very close.

Figures

FIG. 55. — Bothriolepis jani Lukševičs, 1986; A, head-shield 100/526 in dorsal view; B, Prm LDM 100/144; C, Pp LDM 100/429; D, La LDM 100/369; E, Nu LDM 100/141; F, paratype, Nu LDM 100/142; G, Nu LDM 100/430; H, PMD LDM 100/83; I, PMD LDM 100/76 in visceral view; J, K, paratype, AMD LDM 100/67 in dorsal and visceral views; L, AMD LDM 100/431; M, ADL LDM 100/121; N, ADL LDM 100/122; O, MxL LDM 100/432; P, MxL 100/377; R, holotype, MxL LDM 100/88. Skujaine River near Klūnas village, Latvia. Tērvete Formation. Abbreviations: La, lateral plate; Nu, nuchal plate; Pp, postpineal plate; Prm, premedian plate; ADL, anterior dorso-lateral plate; AMD, anterior median dorsal plate; MxL, mixilateral plate; PMD, posterior median dorsal plate. Scale bar: 10 mm.

FIG. 56. — Bothriolepis jani Lukševičs, 1986; A, head-shield LDM 100/526; B, Prm LDM 100/427; C, Pp LDM 100/429 in visceral view; D-G, Nu; D, LDM 100/430 in dorsal view; E, LDM 100/142 in dorsal view; F, G, LDM 100/372 in dorsal and visceral views. Skujaine River near Klūnas village, Latvia. Tērvete Formation. Abbreviations: La, lateral plate; Nu, nuchal plate; Pn, paranuchal plate; Pp, postpineal plate; Prm, premedian plate; cr.o, median occipital crista; cr.pto, postorbital crista; cr.tv, transverse nuchal crista; csl, central sensory line groove; d.end, opening of canal for endolymphatic duct; fe.orb, orbital fenestra; g, paired pits on Pp; ifc1, principal section of infraorbital sensory line on head-shield; ifc2, branch of infraorbital sensory line diverging on La; mc, lateral corner; mp, middle pit-line groove; mppr, posterior process on Nu; mr, median ridge of Pp; nm, obtected nuchal area; npp, postpineal notch; ood, oticooccipital depression; pc, postero-lateral corner; socc, supraoccipital cross-commissural pit-line groove; sot, supraotic thickening. Scale bar: 5 mm.

FIG. 57. — Bothriolepis jani Lukševičs, 1986, AMD; A, B, LDM 100/67 in dorsal and visceral views; C, LDM 100/119 in dorsal view; D, LDM 100/431 in dorsal view.Skujaine River near Klūnas village, Latvia. Tērvete Formation. Abbreviations:ADL, anterior dorso-lateral plate; AMD, anterior median dorsal plate; MxL, mixilateral plate; PMD, posterior median dorsal plate; alr, postlevator thickenings; cf.ADL, area overlapping ADL; cf.MxL, area overlapping MxL; cr.pl, postlevator crista; dlg2, posterior oblique dorsal sensory line groove; dma, tergal angle; dmr, dorsal median ridge; f.retr, levator fossa; grm, ventral median groove; lc, lateral corner; mvr, median ventral ridge; oa.MxL, area overlapped by MxL; oa.PMD, area overlapped by PMD; pt1, anterior ventral pit. Scale bar: 5 mm.

FIG. 58. — Bothriolepis jani Lukševičs, 1986; A-D, PMD; A, B, LDM 100/83 in dorsal and visceral views; C, LDM 100/84 in visceral view; D, LDM 100/80 in dorsal view; E, F, ADL; E, LDM 100/121; F, LDM 100/122. Skujaine River near Klūnas village, Latvia. Tērvete Formation. Abbreviations: ADL, anterior dorso-lateral plate; AMD, anterior median dorsal plate; MxL, mixilateral plate; PMD, posterior median dorsal plate; cf.AMD, area overlapping AMD; cf.MxL, area overlapping MxL; cr.tp, crista transversalis interna posterior; dlm, dorsal lamina; dlr, dorso-lateral ridge; dmr, dorsal median ridge; l, lateral corner of PMD; lcg, main lateral line groove; oa.AMD, area overlapped by AMD; pa, posterior corner; plc, postero-lateral corner; pma, posterior marginal area; pnoa, postnuchal ornamented corner; pro, processus obstans; pt2, posterior ventral pit; tb, ventral tuberosity. Scale bar: 5 mm.

FIG. 59. — Bothriolepis jani Lukševičs, 1986; A-D, MxL in dorsal view; A, LDM 100/87; B, LDM 100/90; C, LDM 100/432; D, holotype LDM 100/88; E, F, AVL; E, LDM 100/433 in ventral view; F, LDM 100/102 in visceral view. Skujaine River near Klūnas village, Latvia. Tērvete Formation. Abbreviations: AMD, anterior median dorsal plate; AVL, anterior ventro-lateral plate; MxL, mixilateral plate; PVL, posterior ventro lateral plate; a.un, unornamented area beneath fossa articularis pectoralis; cf.AVL, area overlapping AVL; cf.PVL, area overlapping PVL; cit1, crista transversalis interna anterior; cit2, transverse thickening; cu, postero-ventral ornamented corner; dlg2, posterior oblique dorsal sensory line groove; dlr, dorso-lateral ridge; f.ax, axillary foramen; f.mp, protractor area of processus brachialis; La, lateral plate; lcg, main lateral line groove; oa.AMD, area overlapped by AMD; oa.PMD, area overlapped by PMD; oa.PVL, area overlapped by PVL;p.br, processus brachialis;prc, prepectoral corner; vlr, ventro-lateral ridge. Scale bar: 5 mm.

FIG. 60. — A-G, Bothriolepis jani Lukševičs, 1986; A, B, AVL LDM 100/98 in ventral and visceral views; C, PVL LDM 100/434; D, CD1 plate LDM 100/144; E, CD1 LDM 100/436; F, ML2 LDM 100/378; G, proximal segment of the pectoral fin LDM 100/435. Skujaine River near Klūnas village, Latvia. Tērvete Formation; H-J, Bothriolepis heckeri n. sp.; H, holotype, AMD plate PIN 835/42 in dorsal view; I, incomplete AMD plate PIN 835/41 in dorsal view; J, incomplete La, Pn and Pmg PIN 835/40 in dorsal view. Malyi Tuder River not far from Bilovo village, Russia. Bilovo Beds(?). Abbreviations: AMD, anterior median dorsal plate; AVL, anterior ventro-lateral plate; CD1, central dorsal plate 1; ML2, lateral marginal plate 2; PVL, posterior ventro lateral plate; La, lateral plate; Pn, paranuchal plate; Pmg, postmarginal plate. Scale bars: 5 mm.

FIG. 61. — Bothriolepis jani Lukševičs, 1986; A, PVL LDM 100/434; B, proximal segment of the pectoral appendage LDM 100/435; C, CD1 LDM 100/130; D, CD1 LDM 100/133; E, CV1 LDM 100/134; F, ML2 LDM 100/378. Skujaine River near Klūnas village, Latvia. Tērvete Formation.Abbreviations: CD1, 2, central dorsal plates 1 and 2; CV1, ventral central plate 1; ML2, lateral marginal plate 2; MM2, mesial marginal plate 2; dc, dorsal corner of lateral lamina; oa.AVL, area overlapped by AVL; PVL, posterior ventro lateral plate; vlr, ventro-lateral ridge. Scale bar: 5 mm.

FIG. 1. — Localities of the Main Devonian Field studied by the author and/or mentioned in the text; 1, Ketleri: Bothriolepis ciecere Lyarskaja in Lyarskaja & Savvaitova, 1974; 2, Pavāri: Bothriolepis ciecere; 3, Bienes: Bothriolepis leptocheira curonica Gross, 1942; 4, Kalnarāji: Bothriolepis maxima Gross, 1933; 5, Kalnamuiža 1: Bothriolepis evaldi Lyarskaja, 1986; 6, Kalnamuiža 2: Bothriolepis sp. (in Amula Formation), Bothriolepis leptocheira curonica (in Eleja Formation); 7, Velna Ala: Bothriolepis maxima, Grossilepis spinosa (Gross, 1942); 8, Klūnas: Bothriolepis ornata Eichwald, 1840, B. jani Luksevics, 1986; 9, Ķurbes: Bothriolepis jani; 10, Ceraukste: Bothriolepis maxima; 11, Lielvārde: Bothriolepis maxima, Bothriolepis sp.; 12, Kaibala: Bothriolepis evaldi; 13, Koknese: Bothriolepis cellulosa (Pander in Keyserling, 1846), Grossilepis tuberculata (Gross, 1941); 14, Pastamuiža: Bothriolepis prima Gross, 1942 and B. obrutschewi Gross, 1942: in Amata Formation; B. cellulosa: in Pļaviņas Formation; 15, Jēkabpils: Bothriolepis sp.; 16, Pelyša: Bothriolepis prima, B. obrutschewi; 17, Vidaga: Bothriolepis traudscholdi Jaekel, 1927; 18, Katleši: Bothriolepis maxima; 19, Kuprava: Bothriolepis cf. maxima; 20, Piskovichi: Bothriolepis obrutschewi; 21, Yam-Tesovo: Bothriolepis prima; 22, Kurskoye Gorodische: Bothriolepis maxima (Obruchev 1947); 23, Luka: Bothriolepis maxima (Obruchev 1947); 24, Bilovo: Bothriolepis sp.; 25, Lyubitino: Bothriolepis ornata (Eichwald 1860); 26, Zarubino: Bothriolepis sp. indet. 1; 27, Paluitsa: Bothriolepis maxima (Ivanov & Khozatsky 1986); 28, Montsevo: Bothriolepis panderi Lahusen, 1880; 29, Stolbovo: Bothriolepis traudscholdi; 30, Andoma Hill: Bothriolepis sp. Dotted line outlines distribution of the Devonian rocks on the subquaternary surface of the Main Devonian Field. The Devonian deposits are not presented to the north of the line, and are covered by the youngest rocks to the south and east.