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Mesungulatum lamarquensis
Taxonomy
Mesungulatum lamarquensis was named by Rougier et al. (2009). Its type specimen is MML-Pv 10, a tooth (right upper molar), and it is a 3D body fossil. Its type locality is Cerro Tortuga, Bajo Trapalcó, which is in a Campanian/Maastrichtian fluvial sandstone/siltstone in the Allen Formation of Argentina.
Synonymy list
| Year | Name and author |
|---|---|
| 2009 | Mesungulatum lamarquensis Rougier et al. p. 227 figs. 2-4f |
| 2024 | Mesungulatum lamarquensis Connelly et al. |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Mesungulatum lamarquensis Rougier et al. 2009
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| G. W. Rougier et al. 2009 | Mesungulatid of similar size to M. houssayi, but without lingual shifting of the stylocone, so that when the molars are oriented with the crown-root boundary horizontal, the buccal wall of the stylocone is more vertical and the apex of the stylocone is almost on the buccal margin of the tooth in M. lamarquensis, rather than more lingual as in M. houssayi. The cingula are broader in M. lamarquensis than in M. houssayi, determining a rectangular outline of the crown (also evident in MML-Pv 11, in spite of having part of the cingulum missing), while in M. houssayi the outline tapers lingually, having a more distinct triangular outline. The mesial and distal cingula culminate lingually in robust and distinct cuspules in M. lamarquensis, but they are not as developed in M. houssayi (this feature is partially responsible for the more rectangular outline of M. lamarquensis). The parastyle is fully independent with a separate
base and a labial surface distinct from the stylocone in relatively unworn specimens of M. houssayi (MACN-RN 03); on the contrary, in M. lamarquensis the parastyle is lower, more rounded, and not so sharply separated from the stylocone by a broad groove. There are two cusps in the metastylar area of M. lamarquensis, a metastyle and a distal cingular cusp; the metastyle is prominent (remnants of which can still been seen in the very much worn MML-Pv 11) and the distal cingular cusp is well differentiated. In contrast, both cusps are poorly developed in M. houssayi and the metastyle is missing in most specimens (although a distinct metastyle is present in MACN-RN 182). The metastyle is more labial and closely appressed in M. houssayi than in M. lamarquensis, where they are almost in line. The mesocrista (sensu Bonaparte, 1990; medianer Grat sensu Martin, 1999; median ridge sensu Kielan-Jaworowska et al., 2004) on the buccal slope of the paracone is poorly developed in M. lamarquensis but is sharp and distinct in unworn specimens of M. houssayi. These differences between M. houssayi and M. lamarquensis are established based on specimens likely to be neither the first nor the last molar, probably M2 (see below). | |
| B. E. Connelly et al. 2024 | Mesungulatum lamarquensis is a mesungulatid of similar size to M. houssayi, differing in the following features (based on M1). The stylocone is located more buccally, with a more vertical wall, and the apex of this cusp is almost on the buccal margin of the tooth. The cingula are broader in M. lamarquensis than in M. houssayi, determining a rectangular outline of the crown, and they culminate lingually in distinct cuspules which are not as developed in M. houssayi. The parastyle is fully independent with a separate base and a buccal surface distinct from the stylocone in relatively unworn specimens of M. houssayi (MACN-RN 03); on the contrary, in M. lamarquensis the parastyle is lower, more rounded, and not so sharply separated from the stylocone by a broad groove. There are two cusps in the metastylar area of M. lamarquensis, a metastyle and a distal cingular cusp; the metastyle is prominent and the distal cingular cusp is well differentiated. In contrast, both cusps are poorly developed in M. houssayi and the metastyle is missing in most specimens. The metastyle is more buccal and closely appressed in M. houssayi than in M. lamarquensis, where they are almost in line. The mesocrista on the buccal slope of the paracone is poorly developed in M. lamarquensis but is sharp and distinct in unworn specimens of M. houssayi. The lower molar of M. houssayi (Bonaparte and Migale, 2015; Rougier et al., 2021) has a metaconid transversely aligned with its protoconid. The cingulid is mostly complete, but interrupted buccally; there are two roots, which are transversely broad and mesio-distally compressed (Bonaparte 1986). The m3 here referred to M. lamarquensis differs from M. houssayi in its bucco-lingually wider mesial cingulid, which projects lingually past the margin of the paraconid and extends to the buccal margin of the protoconid. |
Measurements
No measurements are available
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| Source: c = class, subp = subphylum, uc = unranked clade | |||||
| References: Hendy et al. 2009, Hopson 1973, Luo et al. 2003, Carroll 1988 | |||||
Age range: base of the Late/Upper Campanian to the top of the Early/Lower Maastrichtian or 83.50000 to 66.00000 Ma
Collections (2 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Late/Upper Campanian - Early/Lower Maastrichtian | Argentina (Río Negro) | Mesungulatum lamarquensis (type locality: 48999 235138) |