Endostructural morphology in hominoid mandibular third premolars: Discrete traits at the enamel-dentine junction

Davies, Thomas W.; Delezene, Lucas K.; Gunz, Philipp; Hublin, Jean‐Jacques; Skinner, Matthew M.

doi:10.1016/j.jhevol.2019.102670

Cited by 13 publications

(15 citation statements)

References 68 publications

(10 reference statements)

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“…Another interesting phenomenon is that of twin dentine horns. Martin et al (2017) noted the presence of this feature in Neanderthal maxillary and mandibular molars, and Davies et al (2019) suggested that some mandibular premolars display a similar feature on the protoconid. Twinned dentine horns are interesting because the patterning cascade model of cusp development predicts that enamel knots should be inhibited from forming in the immediate vicinity of one another ( Jernvall, 2000 ; Jernvall & Thesleff, 2000 ), suggesting that twinned dentine horns may result from a single enamel knot, rather than two separate enamel knots.…”

Section: Discussionmentioning

confidence: 99%

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars

Davies

Alemseged

Gidna³

et al. 2021

PeerJ

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Studies of hominin dental morphology frequently consider accessory cusps on the lower molars, in particular those on the distal margin of the tooth (C6 or distal accessory cusp) and the lingual margin of the tooth (C7 or lingual accessory cusp). They are often utilized in studies of hominin systematics, where their presence or absence is assessed at the outer enamel surface (OES). However, studies of the enamel-dentine junction (EDJ) suggest these traits may be more variable in development, morphology and position than previously thought. Building on these studies, we outline a scoring procedure for the EDJ expression of these accessory cusps that considers the relationship between these accessory cusps and the surrounding primary cusps. We apply this scoring system to a sample of Plio-Pleistocene hominin mandibular molars of Paranthropus robustus, Paranthropus boisei, Australopithecus afarensis, Australopithecus africanus, Homo sp., Homo habilis and Homo erectus from Africa and Asia (n = 132). We find that there are taxon-specific patterns in accessory cusp expression at the EDJ that are consistent with previous findings at the OES. For example, P. robustus M1s and M2s very often have a distal accessory cusp but no lingual accessory cusp, while H. habilis M1s and M2s show the opposite pattern. The EDJ also reveals a number of complicating factors; some apparent accessory cusps at the enamel surface are represented at the EDJ only by shouldering on the ridges associated with the main cusps, while other accessory cusps appear to have little or no EDJ expression at all. We also discuss the presence of double and triple accessory cusps, including the presence of a double lingual accessory cusp on the distal ridge of the metaconid in the type specimen of H. habilis (OH 7–M1) that is not clear at the OES due to occlusal wear. Overall, our observations, as well as our understanding of the developmental underpinnings of cusp patterning, suggest that we should be cautious in our comparisons of accessory cusps for taxonomic interpretations.

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Section: Discussionmentioning

confidence: 99%

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars

Davies

Alemseged

Gidna³

et al. 2021

PeerJ

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“…7a,d), 14 but the lingual margin is uninterrupted at the EDJ (Fig. 7g; Davies et al, 2019). The mesial and distal margins also both appear to have been uninterrupted (there is no evidence of interruption at the EDJ).…”

Section: Descriptionmentioning

confidence: 90%

The morphology of the Late Pleistocene hominin remains from the site of La Cotte de St Brelade, Jersey (Channel Islands)

Compton

Skinner

Humphrey

et al. 2021

Journal of Human Evolution

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“…2012, 2014; Zanolli & Mazurier 2013; Davies et al . 2019; Détroit et al . 2019) given that it provides highly‐diagnostic additional information for taxonomic identification (Smith et al .…”

Section: Discussionmentioning

confidence: 99%

Dryopithecine palaeobiodiversity in the Iberian Miocene revisited on the basis of molar endostructural morphology

et al. 2021

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Extensive fieldwork at Abocador de Can Mata (north‐east Iberian Peninsula) has uncovered a previously unsuspected diversity of catarrhine primates in the middle Miocene (12.5–11.6 Ma) of Europe. However, the distinction of the great ape genera Pierolapithecus and Anoiapithecus from Dryopithecus (supported by craniodental differences) has been disputed by some authors. Here we revisit the diversity of great apes (dryopithecines) from the Iberian Miocene based on molar 3D endostructural morphology (relative enamel thickness, enamel distribution, and enamel–dentine junction (EDJ)). Using microtomography, we inspected an extensive sample of 49 hominoid molars representing at least five species from 12 localities. 2D and 3D relative enamel thickness values indicate that Dryopithecus and ‘Sivapithecus’ occidentalis (species inquirenda) display the thinnest and thickest enamel, respectively, while the remaining taxa (Hispanopithecus, Anoiapithecus, Pierolapithecus) show intermediate values. Upper molar enamel distribution maps exhibit a similar pattern in P. catalaunicus, A. brevirostris, D. fontani, H. laietanus and H. crusafonti whereas for the lower molars they reveal differences between H. laietanus and H. crusafonti. Lower molar enamel distribution and EDJ morphology of ‘S.’ occidentalis support the distinction of this species but do not resolve whether it is a junior synonym of Anoiapithecus brevirostris or Pierolapithecus catalaunicus. Overall our results support the distinction of middle Miocene dryopithecins from late Miocene hispanopithecins, the distinction of Pierolapithecus and Anoiapithecus from Dryopithecus among the former, and the distinct species status of H. crusafonti compared to H. laietanus among the latter. Our results highlight the potential of inner tooth morphology for hominoid alpha‐taxonomy.

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Endostructural morphology in hominoid mandibular third premolars: Discrete traits at the enamel-dentine junction

Cited by 13 publications

References 68 publications

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars

Accessory cusp expression at the enamel-dentine junction of hominin mandibular molars

The morphology of the Late Pleistocene hominin remains from the site of La Cotte de St Brelade, Jersey (Channel Islands)

Dryopithecine palaeobiodiversity in the Iberian Miocene revisited on the basis of molar endostructural morphology

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