Four new Early Devonian ischnacanthid acanthodians from the Mackenzie Mountains, Northwest Territories, Canada: an early experiment in dental diversity

Abstract

The Early Devonian (Lochkovian) Man On The Hill (MOTH) locality in the Northwest Territories has yielded hundreds of exquisitely preserved specimens of over 72 different species of early vertebrates, greatly increasing our understanding of the diversity of this period. In this paper, we describe three new genera comprising four new species of ischnacanthid acanthodian, based on their dentigerous jaw bones and teeth. This taxonomic diversity reflects some of the diversity of dentition found among ischnacanthiform acanthodians at the MOTH locality, in contrast to their highly conservative body forms. This high diversity of related forms suggests an early radiation in jaw and tooth morphology in Early Devonian ischnacanthiform acanthodians in this region. All ischnacanthiform specimens from MOTH were originally assigned to Ischnacanthus gracilis. However, study of the unique jaw and tooth morphology of MOTH ischnacanthiform specimens indicates that it is unlikely that Ischnacanthus was present at the MOTH locality.http://zoobank.org/urn:lsid:zoobank.

Precise occlusion and trophic niche differentiation indicate specialized feeding in Early Devonian jawed vertebrates

“…Tightly interlocking teeth have been suggested as an indicator of macrophagy in crocodylians (Young et al 2012), and the anterior and posterior flanges would have formed an almost continuous slicing or cutting surface. The teeth of E. rugosus also have longitudinal ridges (Blais et al 2015), which, in other taxa, have been suggested to indicate the presence of plicidentine (Meunier et al 2014). Plicidentine is currently unknown in ischnacanthiforms, and a histological analysis of the teeth would be required to determine whether these ridges are the result of infolding of the dentine in Euryacanthus.…”

“…To reconstruct the broken teeth and missing jaw cartilage of UALVP 48487, UALVP 45078, and UALVP 41920 were used as references (fig. 5 in Blais et al 2015). The blank labial side of UALVP 45648 was also filled in as flat, as it was reconstructed on the lingual side only and not prepared out of its matrix because of its status as the holotype of the species.…”

“…In particular, UALVP 45050 ( fig. 3D in Blais et al 2015) was used as a reference to reconstruct the broken teeth of UALVP 45648. To reconstruct the broken teeth and missing jaw cartilage of UALVP 48487, UALVP 45078, and UALVP 41920 were used as references (fig.…”

“…In addition to many agnathan taxa, acanthodians and stem chondrichthyans have been recovered (Bernacsek and Dineley 1977;Gagnier et al 1999;Hanke et al 2001aHanke et al , 2001bHanke 2002;Hanke andWilson 2004, 2006;Blais et al 2011Blais et al , 2015Scott and Wilson 2012), including nearly complete articulated specimens of ischnacanthiform acanthodians (Fig. 1).…”

“…In this study, articulated pairs of upper and lower jaws from two different species of ischnacanthiform from the MOTH locality, Euryacanthus rugosus (Blais et al 2015) and Tricuspicanthus gannitus (Blais et al 2015) (Fig. 2), were isolated from the surrounding matrix and scanned using micro-computed tomography (μCT) to create three-dimensionally sculpted reconstructions.…”