Neohelos davidridei, Black & Archer & Hand & Godthelp, 2013
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publication ID |
https://doi.org/ 10.4202/app.2012.0001 |
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persistent identifier |
https://treatment.plazi.org/id/03D987C9-6521-FFB0-FF6D-FB09BD88E34E |
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treatment provided by |
Felipe |
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scientific name |
Neohelos davidridei |
| status |
sp. nov. |
Neohelos davidridei sp. nov.
Figs. 3 View Fig , 4 View Fig , Table 1.
2000 Neohelos sp. C ; Murray et al. 2000b: 72–76, figs. 52–54.
Etymology: In honour of the late William David Lindsay Ride AM (1926–2011), former Director of the Western Australian Museum, Chief Research Scientist of CSIRO, explorer of remote Central Australia, brilliant vertebrate paleontologist, mammalogist, taxonomist and valued mentor to his students.
Holotype: QM F40175, partial tooth row consisting of an isolated right dP3, P3, M1–2 and maxilla fragments.
Type locality: Jaw Junction Site, Faunal Zone C deposits, Riversleigh World Heritage Area fossil deposit, Queensland, Australia.
Type horizon: The JJ Site is at the stratigraphically highest (201 m) level of the northern section of the Gag Plateau sequence ( Creaser 1997). On the basis of stratigraphy and stage−of−evolution biocorrelation, the JJ Site is thought to be one of the youngest FZ C deposits and approximately Middle Miocene in age.
Referred specimens.—From JJ Site: QM F40174, Lm1 and dentary fragments; QM F40176, Lm2–3 and LM4; QM F40177, Ri1; QM F40178, RP3; QM F40179, Rm2; QM F40182, Rp3; QM F40180, partial Rm1; QM F40181, RM1 missing most of metaloph; QM F40186 (NTM P91168−2), RM3.
Diagnosis.— Neohelos davidridei differs from other species of Neohelos in the following combination of features: higher crowned; p3 lacking anterior crest with a gently sloping anterior protoconid face; p3 that lacks a distinct division between its anterior and posterior moieties; P3 with incipient division of the parametacone into its respective cusps; P3 parastyle larger and more separated from the parametacone base, resulting in a more elongate premolar overall. Neohelos davidridei differs from Ne. solus and Ne. tirarensis in having larger molars. Neohelos davidridei differs from Ne. solus in: having proportionately broader molars with less arcuate protolophs and less convex paracone and metacone buccal margins; lacking the posterolingual crest that ascends the metaloph on M1–2; having a continuous, arcuate lingual cingulum on M1; and in having a lower paralophid and broader protolophid on m1.
Description
Holotype.— dP3 ( Fig. 3 View Fig ): The deciduous P3 is a small, subtriangular tooth with four primary cusps including an anterior paracone, posterior metacone, anterolingual protocone and posterolingual hypocone. A possible fifth cusp, a weak parastyle, may have been situated at the anterior border of the tooth, however, this region is broken. The paracone is the tallest cusp, followed by the metacone, protocone and hypocone. The apices of the paracone and metacone are in line anteroposteriorly, just lingual to the midline of the tooth, and separated by a V−shaped valley. The protocone and hypocone are situated on the lingual margin, which is swollen and ovate— unlike the buccal margin, which is linear. Weak lingual crests extend from the apices of the paracone and metacone into the
http://dx.doi.org/10.4202/app.2012.0001
shallow longitudinal valley separating them from the protocone. A weak postmetacrista extends to the posterior tooth margin, becoming cuspate at this point. The posterolingual cingulum is weak and connects this posterior cuspule with a small hypocone. A buccal cingulum is absent. The anterior parastylar region is distinctly emarginated on the anterolingual crown base.
P3 ( Fig. 3 View Fig ): P3 is a sub−ovate, quadritubercular tooth consisting of a large central parametacone, a well−developed anterior parastyle, a lingual protocone and a posterolingual hypocone. The parametacone is the tallest cusp, followed by the parastyle, protocone and hypocone. The protocone and hypocone are pyramidal in occlusal view. The premolar exhibits distinct anterior and posterior moieties and is widest across the protocone. The parametacone shows incipient differentiation into a respective paracone and metacone. The paracone apex is distinguished from that of the metacone by its greater height. Additionally, a shallow fissure extends down the buccal tooth margin from the point of division of the respective cusps. A lingual fissure is also present. The distinct paracone apex is connected to the blade−like apex of the metacone by a short ridge. The parametacone is pyramidal in occlusal view with distinct anterior, buccal and lingual faces. The large, erect parastyle is situated at the anterior tooth margin and separated from the parametacone by a relatively deep transverse valley. The lingual surfaces of the parametacone are steep and almost vertical. The buccal faces slope more gently towards the buccal tooth margin. A small anterolingual basin is bordered by the posterolingual base of the parastyle, the anterolingual base of the parametacone and the anterior base of the protocone. The apex of the parastyle lies directly anteriorly opposite the apex of the parametacone. A well−developed protocone lies opposite and slightly anterior to the parametacone apex on the lingual tooth margin. Two faint, transversely directed cristae from the apices of the parametacone and protocone meet in the longitudinal valley separating these cusps. A small hypocone lies posterior and slightly lingual to the protocone. A well−developed post−parametacrista extends posteriorly and slightly buccally to the posterior tooth margin and is continuous with the lingual and buccal cingula. The buccal cingulum curves anterobuccally around the base of the crown. A small mesostyle exists as a swelling on the buccal margin at a point opposite the parametacone. A continuous posterolingual cingulum extends from the postparametacrista in an anterolingual direction to the hypocone apex. It then travels into the valley between the hypocone and protocone, resulting in the formation of a deep basin, and continues up to the protocone apex and anteriorly into the anterolingual basin, and up to the parastyle apex. A slight swelling of the lingual cingulum at the anterolingual base of the protocone represents a small protostyle.
QM F40178 ( Fig. 4 View Fig ), another RP3, is similar overall to QM F40175, except for the following differences: the protocone is taller with a broader lingual base; the incipient division of the parametacone is less distinct and the fissure extending down its buccal face is absent; the parastyle apex is more buccally positioned; and the posterobuccal cingulum and mesostyle are better developed.
M1 ( Fig. 3 View Fig ): The M1 is relatively square in occlusal outline, although the metaloph is slightly wider than the protoloph. The tips of the lophs are slightly crescentic and overhang their bases anteriorly. The parastyle and metastyle are well developed, but positioned low on the crown. The parastyle is dominated by a distinct crescentic ridge that becomes continuous with the anterior cingulum. The metastyle is more distinctly cuspate than the parastyle and is continuous with the posterior cingulum. A short cleft separates the metastyle from the moderately developed postmetacrista. A weaker postparacrista extends down the posterobuccal face of the paracone, becoming more distinct at the buccal border of the transverse median valley. The transverse median valley is open buccally, yet closed lingually by a short, crescentic lingual cingulum. The anterior and posterior cingula are well developed, but not continuous with the lingual cingulum. Instead, they terminate at the anterolingual and posterolingual bases of the protocone and metaconule, respectively. The anterior cingulum becomes mildly cuspate midway along its length where it rises dorsally.
M2 ( Fig. 3 View Fig ): M2 similar to M1, except that: it is larger; wider anteriorly than posteriorly with a corresponding wider protoloph; the parastyle and metastyle are reduced; the postparacrista and postmetacrista are absent; and the lingual cingulum is reduced and less arcuate.
Referred material.— M3: QM F40186, unworn enamel cap missing the posterolingual tooth corner including the metaconule. It is similar to the M2 of the holotype, except that: the metaloph is reduced both in height and width, resulting in a trapezoidal tooth outline; the protoloph is wider and more crescentic; and a metastyle is absent.
M4: QM F40176, unworn enamel cap similar to M3, except that: it is lower crowned; the metaloph is further reduced in both width and height and is more convex buccally; the parastyle, metastyle and posterior cingulum are absent; the lophs are less anteriorly overhanging; and the transverse median valley is wider and more open both buccally and lingually.
i1 ( Fig. 4 View Fig ): QM F40177, a right i1, is heavily worn and missing its root. It is a deep (maximum depth 18.5 mm), broadly lanceolate tooth with a 5 mm section of dentine exposed from its medially curved tip to its posterior border. A series of longitudinal ridges cross the enamel medially. A fine ridge of enamel overhangs the exposed dentine dorsally. The maximum mediolateral thickness of the incisor is 11.0 mm.
p3 ( Fig. 4 View Fig ): QM F40182, a right p3, is a large, sub−triangular, unworn tooth that tapers anteriorly. It is dominated by a single central cuspid, the protoconid (13.4 mm high). The anterior face of the protoconid slopes gently and evenly at an angle of 45 ° to the base of the crown. An anterior protoconid crest is absent. The posterior protoconid crest slopes steeply for 4 mm, then extends almost horizontally to the posterior tooth margin, becoming continuous with a well−defined arcuate posterolingual cingulum. A lingual, non−crested buttress extends vertically from the protoconid apex to the base of the crown, defining the lingual fossa anteriorly. A weak posterobuccal cingulum exists as a swelling at the posterobuccal tooth corner and fades into the base of the crown. The lingual and buccal tooth margins curve gently from anterior to posterior. Consequently, there is no division of the tooth into anterior and posterior moieties.
m1: QM F40174 ( Fig. 4 View Fig ), a left, nearly complete, sub−rectangular, unworn m1 that is missing its anterior border and enamel from the lingual face of the metaconid and buccal face of the protoconid. The protolophid is narrower (10.3 mm) than the hypolophid (12.9 mm) and slightly more crescentic. A strong, steep paralophid extends ventrally from the protoconid to the base of the crown. In QM F40180, which preserves the anterior tooth border, the paralophid is continuous with a short cingulum. A small pocket is formed between the steep anterior face of the protolophid and the anterior cingulum. A weaker anterobuccal cingulum curves around the base of the crown from its junction with the paralophid, but its extent cannot be determined. A weak premetacristd and prehypocristid fade down the anterior faces of their respective cuspids. A low, irregular posterior cingulum rises towards the tooth midline. The hypoconid is shorter than the entoconid. The transverse median valley is open lingually and buccally, and is V−shaped in lateral view.
m2: QM F40174 and QM F40179 are both left m2s. The m2 is a sub−rectangular tooth that is similar to m1, except for the following: it is larger overall; the paralophid is absent; the protolophid is wider than the metalophid; both lophids are more crescentic and the protolophid is more curved than the hypolophid; the transverse valley is broader, more open and U−shaped in lateral view; and the tips of the lophids overhang their bases slightly posteriorly.
m3–4: QM F40176, left unworn enamel caps of m3–4. m3 is similar to m2, except for the following: it is larger; the protolophid is wider; the transverse median valley is broader and U−shaped in lateral view. m4 is similar to m3, except for the following: the protolophid is wider but lower; the metalophid is reduced; and the anterior cingulum is less lingually extensive.
Geographic and stratigraphic range.—Middle Miocene; JJ Site, Riversleigh World Heritage Area, northwestern Queensland.
http://dx.doi.org/10.4202/app.2012.0001
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Neohelos davidridei
| Black, Karen H., Archer, Michael, Hand, Suzanne J. & Godthelp, Henk 2013 |
Neohelos sp. C
| Murray, P. & Megirian, D. & Rich, T. & Plane, M. & Black, K. & Archer, M. & Hand, S. & Vickers-Rich, P. 2000: 72 |