taxonID	type	description	language	source
03EBCE03BF5FFFBA1D54FE710785FB79.taxon	materials_examined	Type species: Arguimus khosbajari Dashzeveg, 1979. Mongolia, Early Cretaceous. Included species: Type species only. Revised diagnosis. — Differs from crown−group Zatheria in having four rather than three molars and in lack of a hypoconulid. Additionally, differs from Peramus Owen, 1871 in the deeper dentary lacking Meckel’s groove and from Tendagurutherium Heinrich, 1998 by lack of Meckel’s groove and coronoid. Differs from Amphitherium de Blainville, 1838 in having smaller number of molars (four versus six−seven), incipient talonid basin on lower molars, and lack of Meckel’s groove. Differs from Nanolestes Martin, 2002 in having four rather than five lower molars, in having an incipient talonid basin, and in a deeper dentary lacking Meckel’s groove. Differs from Minimus Sigogneau−Russell, 1999 by longer talonid on lower molars. Differs from Chunnelodon Ensom and Sigogneau−Russell, 1998 in having a shorter talonid with incipient talonid basin and lower metaconid on m 1. Differs from Vincelestes Bonaparte, 1986 in having a larger number of lower premolars (five versus two) and molars (four versus three), the last premolar smaller than m 1, and longer molar talonids.	en	Lopatin, Alexey, Averianov, Alexander (2006): Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51 (2): 339-349, DOI: 10.5281/zenodo.13644098
03EBCE03BF5FFFBD1D54FB5A033DFADC.taxon	description	Figs. 1 – 6.	en	Lopatin, Alexey, Averianov, Alexander (2006): Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51 (2): 339-349, DOI: 10.5281/zenodo.13644098
03EBCE03BF5FFFBD1D54FB5A033DFADC.taxon	materials_examined	Holotype: PSS 10 − 15, left dentary fragment with p 4 – 5, m 1 – 3, and alveoli for p 2 – 3 and m 4 (see discussion for interpretation of the dental formula).	en	Lopatin, Alexey, Averianov, Alexander (2006): Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51 (2): 339-349, DOI: 10.5281/zenodo.13644098
03EBCE03BF5FFFBD1D54FB5A033DFADC.taxon	description	Description. — The dentary was apparently elongate, with the mandibular symphysis terminating between p 3 and p 4 (PSS 10 − 15 and 10 − 31) or under the anterior root of p 4 (PIN 3101 / 364 and 400; Figs. 1 D and 2 D). There is a distinct nutrient foramen within the mandibular symphysis in PIN 3101 / 364 (Fig. 1 D). The dentary deepens considerably in the molar region, being approximately twice as deep as the unworn m 2 in PIN 3101 / 364 (Fig. 1 D and F). The labial margins of the tooth alveoli are distinctly lower than their lingual margins, and this height differential increases anteriorly (Figs. 1 D, F, 2 D, F, 3 A, B, 4 A 3, A 4, B 3, B 4). The posterior mental foramen is situated under the anterior root of p 4 (PIN 3101 / 400; Fig. 2 F), posterior root of p 4 (PSS 10 − 31), anterior root of p 5 (PSS 10 − 15), between the roots of p 5 (PIN 3101 / 364; Fig. 1 F), or between the roots of m 1 (PIN 3101 / 106; Fig. 3 A). There are two anterior mental foramina: under the anterior root of p 4 (PSS 10 − 15) or the posterior root of p 3 (PIN 3101 / 364; Fig. 1 F), and under the posterior root of p 2 (PSS 10 − 15, PIN 3101 / 364; Fig. 1 F). In all specimens there are no traces of the Meckel’s groove. The coronoid process (partially preserved only in PIN 3101 / 108, Fig. 4 A) is rather steep and close to m 4, with a strong coronoid crest. Inside the masseteric fossa, at the base of the posterior side of the coronoid crest in PIN 3101 / 108, is a cleft−like depression with a labial mandibular foramen at the alveolar level leading to the mandibular canal (Fig. 5). The mandibular canal is large, as evident from its section in several specimens. On (C, stereopair) views. D – F. The whole specimen in lingual (D), occlusal (E), and labial (F) views. Scale bars 1 mm. LOPATIN AND AVERIANOV — PRETRIBOSPHENIC MAMMAL ARGUIMUS 343 m 2 m 1 m 4 m 3 PIN 3101 / 108 (Fig. 4 A 4) there is neither a coronoid bone preserved, nor a distinct facet for this bone, but there is a very faint bump−like structure on the medial side of the coronoid process at the alveolar level, which is referred to as a rugosity of uncertain meaning after Wible et al. (2004). Anterior premolars are not known, their alveoli are best preserved on PSS 10 − 31 and PIN 3101 / 364 (Fig. 1 E, F), and interpreted as double−rooted p 1 – 3. Judging from the alveoli on PIN 3101 / 364, p 2 was larger than p 1 and p 3. The p 4 – 5 are preserved on the holotype and PSS 10 − 31 and are heavily worn in both specimens. Both posterior premolars are similar premolariform in structure. The p 5 is intermediate in height between p 4 and m 1. The anterior accessory cusp was apparently present on both premolars (better developed on p 4) but worn in known specimens. The posterior accessory cusp is distinct. The p 5 widens considerably posteriorly, p 4 is of similar width through out its entire length. The lingual cingulid is not distinct but the bulbous lingual base of the crown is worn on p 4 and especially on p 5. The roots of all cheek teeth are set vertically in the dentary. On molars the labial side of the crown is higher than the lingual and the crowns are tilted somewhat lingually from the vertical plane. The trigonid angle of molars is largest on m 1, decreases on m 2 and m 3 and slightly increases on m 4 (Table 1). This angle decreases considerably with wear by the removing of dentine from the paracristid anteriorly and protocristid posteriorly, as evident from m 1 and m 2 (Table 1). Lower molars have a short talonid with a single cusp (hypoconid) and variably developed interlocking system. The best developed interlocking is between m 1 and m 2 on PIN 3101 / 364 (Fig. 1 C), where the m 1 talonid is deeply inserted between the well developed cuspules e (anterolingual) and f (anterolabial). A less pronounced interlocking is present between m 1 and m 2 on PIN 3101 / 106 and between m 2 and m 3 on PIN 3101 / 108 (Figs. 3 C and 4 A 1). Cuspule e is small and ridge−like in both specimens and cuspule f is absent on PIN 3101 / 106. The m 1 is the most distinctive tooth of the lower molars, being “ partially molariform ”. The protoconid is lower than on m 2. The paraconid is very small and low, placed almost anteriorly to the protoconid. The metaconid is higher, but still small and placed posterolingually to the protoconid. There is a short and almost vertical distal metacristid. It is seen only on unworn specimens (PIN 3101 / 364 and 400, Figs. 1 C and 2 C) and rapidly becomes obliterated by wear. On PIN 3101 / 400 the talonid of m 1 is relatively longer and with a better developed hypoconid than on m 1 of PIN 3101 / 364. A small incipient talonid basin is preserved only in unworn m 1 ’ s of PIN 3101 / 364 and 400 (Figs. 1 C and 2 C) and partially preserved on the worn m 1 of PIN 3101 / 106 (Fig. 3 C). The entocristid, bordering the talonid basin posteriorly and lingually, is distinct on PIN 3101 / 400, but much weaker on PIN 3101 / 364 (Figs. 1 C and 2 C). On m 2 – 4 (m 2 is unworn in PIN 3101 / 364; Fig. 1) the paraconid and metaconid are of similar height and distinctly higher than on m 1. The talonid of m 2 – 4 is relatively shorter than on m 1. The m 4 is distinctly lower and somewhat shorter than m 3 (PIN 3101 / 108: Fig. 4 A). The known specimens show progressive wear of molars and can be grouped into several stages: (1) PIN 3101 / 364 (m 1 – 2): completely unworn molars (Fig. 1). (2) PIN 3101 / 400 (m 1): wear facet 3 produced by the postparacrista of upper molar is developed along the distal metacristid and at the bottom of hypoflexid; there are no wear facets 1 or 2 (Fig. 2 C). (3) PIN 3101 / 106 (m 1 – 2), PSS 10 − 15 (m 2 – 3), and PSS 10 − 31 (m 1): vertical wear facet 3 along the distal metacristid is extensive, removing a considerable part of the labial tooth crown and coming down the crown to near the crown−root junction (on m 2 of PIN 3101 / 106 the pulp cavity is visible through a thin dentine layer); protocristid and paracristid are worn by more horizontal wear facets 1 and 2 produced respectively by the preparacrista and postmetacrista of the upper molar. On m 1 of PSS 10 − 31 the horizontal component of wear facet 1 is extensive, while the paracristid is almost unworn. On m 1 of PIN 3101 / 106 the paracristid is little worn (Fig. 3 C). (4) PIN 3101 / 108 (m 3 – 4): there are extensive vertical wear facets 1 and 3 along the protocristid and distal metacristid, occupying almost all the space of the hypoflexid and coming down to the root labially; a horizontal wear facet 2 is extensive and a vertical component of this facet appears on the labial side along the paracristid. Along the posterolabial side of the hypoconid on m 4 of PIN 3101 / 108 there is a distinct wear facet 4 produced by the premetacrista of M 4 (Fig. 4 A 1). (5) PIN 3101 / 107 (m 2) and PSS 10 − 15 (m 1): trigonid cusps are almost completely worn down, the hypoflexid is deeply excavated by the vertical wear facets 1 and 3 (exposing the pulp cavity on PIN 3101 / 107; Fig. 4 B 1). None of the studied specimens shows unequivocal attritional wear facets within the talonid on the lingual slope of the hypoconid. This would suggest the absence of a well developed protocone on upper molars. Measurements. — See Table 2.	en	Lopatin, Alexey, Averianov, Alexander (2006): Revision of a pretribosphenic mammal Arguimus from the Early Cretaceous of Mongolia. Acta Palaeontologica Polonica 51 (2): 339-349, DOI: 10.5281/zenodo.13644098
