Bothriolepis sp.
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publication ID |
https://doi.org/ 10.4202/app.00015.2013 |
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persistent identifier |
https://treatment.plazi.org/id/038EB778-B347-FFA9-FF20-FCA2500A8B31 |
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treatment provided by |
Felipe |
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scientific name |
Bothriolepis sp. |
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Fig. 4 View Fig .
Material.— AMD: PALULG-2011.12.15.13, PALULG-2011.12.15.14,PALULG-2011.12.15.15,UCL-P.V.L.10.646, UCL.P.V.L.10.697; MxL: UCL-P.V.L.10.624; AVL: PAL- ULG-2011.12.15.16;?CV1: PALULG-2011.12.15.17. From Modave quarry, also known as Pont-de-Bonne, Bonne Valley, Liège Province, Belgium, upper part of the Evieux Formation, Famennian, Upper Devonian.
Description
Trunkshield.— Anterior median dorsal plate, AMD ( Fig. 4A, B View Fig ): This plate is as long as wide. Externally, it is smoothly arched. The tergal angle is situated slightly in front of the transition between the anterior and middle thirds of the plate. It is of roughly 45°. The posterior oblique dorsal sensory line grooves are clearly observed. The dorsal median ridge is weakly defined and runs from the tergal angle to the posterior margin. The anterior margin is concave and slightly longer than the posterior one. The external postlevator process is well defined and prominent. The lateral and the postero-lateral corners are clearly observable. The posterior median process is well defined. The maximal width of the plate is at the lateral corners. The width at the postlevator processes is slightly inferior. The anterior part of the lateral margin is twice the length of the posterior part. Internally, the postlevator thickenings are low but well denoted, the triangular-shaped levator fossa gently deep and the anterior ventral pit oval and tiny. The anterior part of the area overlapping ADL is well extended. These internal characters are only observable on the largest AMD ( Fig. 3A View Fig 2), which is the only one being preserved in internal view.
Mixilateral plate, MxL ( Fig. 4C View Fig ): The lateral lamina is not preserved and the dorsal lamina presents a damaged surface. The anterior part of the dorso-medial margin is straight and measures half the length of the posterior part. The dorso-medial corner, that separates them, is well defined.The length of the straight posterior margin equals the length of the slightly convex anterior margin. The posterior oblique dorsal sensory line groove is slightly marked and runs from the dorso-medial corner area to the limit between the anterior and middle thirds of the plate. Such a course is unusual for the posterior oblique dorsal sensory line. Thus, the identification of this plate could be misinterpreted.
Anterior ventro-lateral plate, AVL ( Fig. 4D View Fig ): This plate is only known in ventral view and is moderately well preserved. The ventral lamina is quite elongated and equals three times its width. The subcephalic division is roughly one third of the total plate length. The crista transversalis interna anterior is well developed, as is also the transverse thickening on the visceral surface and the depression between both cristae. The lateral lamina is so compressed that it is impossible to evaluate the angle made posteriorly by the ventro-lateral ridge. The pectoral joint area is observable but quite difficult to interpret because of the bad preservation. Nevertheless, quite a large axillary foramen is observable.
Pectoral fin.— Only one element of the pectoral fin is preserved. It is a fragment of the proximal segment, a ventral or a dorsal central plate 1 ( Fig. 4E View Fig ). The only element allowing this attribution is the rounded articular surface. An accurate attribution is impossible due to the very poor preservation.
Ornament.— The ornament is the same for all the plates described above, that is, a reticulate ornament composed of a smooth and regular network of interconnecting ridges.
Remarks.— The material described above is not sufficient to erect a new species, because there is not enough material, and because much of it is considered as belonging to half-mature individuals. This is the case of 5 out of 6 AMDs. Actually, they display several juvenile characters such as the presence of oblique transverse depressions and oblique transverse ridges, a developed posterior median process and a reticulate ornament. The length of these plates does not exceed 1.5 cm. However, they also display adult characters, such as a weak dorsal median ridge and the absence, at least not observable, of anterior oblique dorsal sensory line grooves. This mixture of juvenile and adult characters argues for half-mature individuals. AMD PALULG-2011.12.15.14 is bigger, roughly twice the width of the other AMDs, but its poor preservation does not provide much information. It could represent either adult material or belong to a different species. They are grouped here for convenience only.
The other trunk and pectoral plates are not in the same size range as the half mature AMDs. However they present exactly the same ornamentation, and this is why they are considered conspecific with the AMDs.
As Stensiö (1948: 211) noticed in the “ Bothriolepinae ”, “certain formations were entirely reduced during the growth, whereas others appeared”. The ornament is also modified during the growth. “In consequence of these changes young and mature individuals always differ considerably from each other in several of their characters” ( Stensiö 1948). Long and Werdelin (1986), Werdelin and Long (1986) and Johanson 1998) quantified these variations. Thus, it seems inappropriate to erect a new species of bothriolepid on the basis of juvenile or half-mature material. Therefore the Bothriolepis material from Modave, which is clearly half-mature (see below) and too fragmentary, is put in open nomenclature in this paper.
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