A new specimen ofHelicoprionKarpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function

Abstract

Lebedev, O.A. 2009. A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function. -Acta Zoologica (Stockholm) 90 (Suppl. 1): 171-182A new Helicoprion bessonowi Karpinsky, 1899 (Chondrichthyes, Eugeneodontiformes) specimen from the Artinskian of Kazakhstan is described. This is the southernmost occurrence of this species in the Cisurals area. Its presence suggests a biogeographical link for this species between the Cisurals and Japan. Residue obtained from chemical preparation of the sample included numerous scales and several teeth, which are tentatively assigned to Helicoprion . This assumption is based upon morphological similarity of the scales to those known in other eugeneodontiforms. Campodus -like teeth might be part of the lateral dentition of Helicoprion . A new reconstruction of the interaction of the lower tooth whorl with the upper jaw dentition is suggested and its function is discussed. It is proposed that there was no symphysial whorl in the upper jaw but its role was played by a rigid cover formed by a series of small teeth at the palatoquadrates. Microscopic study of the tooth crown surface revealed scratch marks, which might have resulted from pressing the food object against the upper jaw. Using extant odontocetans as an ecological model led to a conclusion that helicoprionids most likely fed on cephalopods and to some extent on fish. This assumption is based upon the concentration of functional dentition in the area of the lower jaw symphysis in both groups of animals.

Chondrichthyans from the Lower Permian of Mechetlino, South Urals

“…Kungurodus obliquus has been found early in the Asselian-Artinskian sequence of the South Urals (Ivanov 2005) and in the Artinskian of the Kazakhstanian Cisurals (Lebedev 2009) but was described also in this paper from the Kungurian. In addition to the Artinskian of the South Urals, species of Sphenacanthus are known from the Viséan to Gzhelian of Great Britain, Spain, Czech Republic, Germany, USA (Iowa), Brazil (Ginter et al 2010); also from the Artinskian, Early Permian of Brazil (Chahud et al 2010); from the Kazanian, Middle Permian of the East European Platform, Russia (Ivanov 2012b); from the Capitanian, Middle Permian of Texas, USA (Ivanov et al 2013).…”

“…The tricuspid teeth dominate collections from other localities of the South Urals (Ivanov 2005). The five-cusped teeth are quite scarce, and have been found in the Artinskian of the Kazakhstanian Cisurals (Lebedev 2009 (Fig. F), South Urals, Bashkortostan, Mechetlino Quarry; A-C -PM SPU 76-1, sample 5919-2b, A -occlusal, B -lingual and C -oblique lateral views; D, E -PM SPU 76-2, sample 5919-2b, D -oblique labial and E -oblique basal views; F -PM SPU 76-3, sample 5919-4b, oblique labial view; G-I -PM SPU 76-4, sample 5919-2b, G -labial and H -occlusal views, I -detail of the base; J-M -PM SPU 76-5, sample 5919-2b, J -lingual and K -basal views, L, M -microtomographic images of tooth, L -cross-section of tooth crown, M -cross-section of tooth base; N -PM SPU 76-6, sample 5919-9a, labial view.…”

The Mechetlino Section (Southern Urals). Paleontological Characteristics

“…Вид Kungurodus obliquus (Ivanov) присутствует также в отложениях кунгурского яруса. Он характерен для ассельского - артинского ярусов Южного и Сред-него Урала , для артинского яруса казахстанского Предуралья [Lebedev, 2009] и впер-вые был обнаружен в кунгурских отложениях раз-реза Мечетлино. Представители рода Sphenacanthus встречаются от визе до гжели Великобритании, Испании, Чехии, Германии, США (Айова), Брази-лии; также характерны для артинского яруса перми ГеолоГический РАзРез мечетлино (Южный уРАл).…”

Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion

“…Earliest models (a -d ) posited the whorl as an external defensive structure, but (e -l ) feeding reconstructions dominate more recent hypotheses. Credits: (a) Woodward [2]; (b) Simoens [11]; (c) Karpinsky [12]; (d ) Obruchev [7]; (e) Van den Berg in Obruchev [7]; (f ) John [8]; (g) Carr [9]; (h) Eaton [4]; (i) Parrish in Purdy [10]; ( j ) Troll in Matsen & Troll [13] based on Bendix-Almgreen [5]; (k) Lebedev [6]; (l ) Troll & Ramsay, this study. Configuration of gill slits and fins based on related fish, e.g.…”

“…His reconstruction placed the tooth whorl at the front midline of elongate lower jaws (figure 1j; [5,13]), and his interpretation of a neurocranial capsule and rostrum led to his assessment that Helicoprion belonged to the Elasmobranchii, an ill-defined group of sharks and rays. Bendix-Almgreen's 'symphyseal' reconstruction ( [6,14]; figure 1j -k) has not been challenged by new physical evidence in the intervening decades. Phylogenetic interpretations of Helicoprion and its spiral-tooth relatives have been less stable; however, most recent analyses based on dental characters have placed Helicoprion among the Euchondrocephali, which include modern chimaera and ratfish [15,16].…”