Progonomys cf. hussaini Cheema et al., 2000
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publication ID |
https://doi.org/ 10.26879/1308 |
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persistent identifier |
https://treatment.plazi.org/id/0382F647-6F15-FF8D-FF49-3C7B9A05FC30 |
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treatment provided by |
Felipe |
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scientific name |
Progonomys cf. hussaini Cheema et al., 2000 |
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Progonomys cf. hussaini Cheema et al., 2000
Figure 5 View FIGURE 5 A-H
Holotype. PMNH 5062 View Materials , left M1.
Type locality. JAL-101, upper portion of the Chinji Formation of the Jalalpur area, Chakwal District, Potwar Plateau, Pakistan.
Referred materials. WIMF /A 4745 right M1 ( Figure 5A View FIGURE 5 ), WIMF /A 4746 left M2 ( Figure 5B View FIGURE 5 ), WIMF /A 4747 left M2 ( Figure 5C View FIGURE 5 ), WIMF /A 4739 right m1 ( Figure 5D View FIGURE 5 ), WIMF /A 4737 left m2 ( Figure 5E View FIGURE 5 ), WIMF /A 4738 left m2 ( Figure 5F View FIGURE 5 ), WIMF /A 4748 left m2 ( Figure 5G View FIGURE 5 ), WIMF /A 4736 right m3 ( Figure 5H View FIGURE 5 ).
Occurrence. Dunera locality, Punjab, India (study area); early Late Miocene of Potwar Plateau, Pakistan.
Description. WIMF/A 4745 ( Figure 5A View FIGURE 5 ) is a right M1 with three roots that is slightly damaged on its buccal side. In occlusal view, the t1 (anterostyle) is placed posterolingually in relation to t2 (lingual anterocone) and t3 (labial anterocone), and weakly connected to the t2. The measured angle between the t1 and the longitudinal axis passing through the centre of the tooth (angle of anterostyle) is ~45°. The t2 and t3 are similar in size. The t4 (enterostyle) is also placed posteriorly compared to t5 (protocone), but is similar in mesiodistal position to t6 (paracone). The enterostyle is weakly connected to t5 (a characteristic that was determined after digitally removing matrix on the occlusal surface) and the measured angle of the enterostyle (angle formed by protocone and enterostyle) is ~72°. The larger t8 (hypocone) is attached to the smaller t9 (metacone). Overall, the cusps are inclined posteriorly and relatively weakly connected transversely. The precingulum is well developed at the mesial end of the tooth and bears a cuspule on its anterolabial margin. The small ridge-like posterior cingulum is connected to the t8, but also separated from it by a small sinus. The t1 and t4 are positioned posteriorly, and laterally compressed and elongated.
The M2s, WIMF/A 4746 ( Figure 5B View FIGURE 5 ) and 4747 ( Figure 5C View FIGURE 5 ), are trapezoidal in occlusal outline. The enterostyle is posterolingual to the protocone and connected to the protocone by a small crest in WIMF/A 4747. In WIMF/A 4746, the potential connection between the enterostyle and protocone is weak. In both specimens, the enterostyle is similar or slightly smaller in size compared to the protocone. The protocone is larger than the paracone, and it is connected by a short crest. An anterostyle is present at the mesiolingual corner of each tooth, continuous with the anterior cingulum. The buccal anterostyle is located just mesial to the paracone and is a small button-shaped cusp in WIMF/A 4747 but more flattened in WIMF/A 4746. On the posterior chevron, a large hypocone is present, connected to the much smaller metacone by a mesiobuccally oriented crest. The hypocone is the largest cusp on both specimens, and the metacone is the smallest. The posterior cingulum is connected to the hypocone but isolated from the metacone by a shallow groove. All cusps are gently inclined posteriorly, and both teeth have three roots.
WIMF/A 4739 ( Figure 5D View FIGURE 5 ) is a right m1 and heavily worn, particularly on its lingual side. Its pre-lobe comprises a labial anteroconid and the remnants of a lingual anteroconid, with the larger labial anteroconid placed slightly distal compared to the lingual anteroconid. The pre-lobe (lingual and labial anteroconids) and the second lobe (protoconid and metaconid) form an “X” shape with a weak longitudinal connection placed towards the lingual side of the tooth, presumably an artifact of the lingual wear. The cuspids of the second lobe, the protoconid and the metaconid, are strongly connected with the protoconid larger and better preserved. The cuspids of the third lobe also have a strong transverse connection, with the buccal cusp (hypoconid) again better preserved compared to the lingual cusp (entoconid). Due in part to the wear on the lingual side, the buccal cusps appear larger and slightly distal relative to the lingual cusps. A buccal cingulum is present, along with prominent C1 and C3 cingular cusps. The posterior cingulum is short and placed towards the lingual side of the tooth; it does not connect to the buccal cingulum. The specimen has two roots.
WIMF / A 4737 ( Figure 5E View FIGURE 5 ) , WIMF / A 4738 ( Figure 5F View FIGURE 5 ) and WIMF / A 4748 ( Figure 5G View FIGURE 5 ) are left m2s. The teeth are rectangular to trapezoidal in outline, tapering distally. The protoconid and metaconid are strongly connected to form the first chevron, whereas the hypoconid and entoconid are connected by a narrower crest and form the second chevron. All three specimens appear to display a labial anteroconid in the mesiobuccal corner of the tooth, particularly visible in the less worn WIMF / A 4737 and WIMF / A 4748 specimens . WIMF / A 4738 is heavily worn compared to the other two teeth, and thus the chevrons appear relatively larger in this specimen. In all three m2s, the first and second chevrons form a distally curving gentle arc, with the second chevron being more transverse (i.e., straight) compared to the first chevron. In both chevrons, the buccal cusps (protoconid and hypoconid) are slightly distal compared to the lingual cusps. In the two relatively unworn/lightly worn specimens ( WIMF / A 4737 and 4748), a buccal cingulum is present with an accessory cuspid (C1) connected to the protoconid. In WIMF / A 4738 , the C1 does not appear to be present ( Figure 5F View FIGURE 5 ). A posterior cingulum is present between the hypoconid and entoconid at the distal end of all three molars. The m2s have two roots .
WIMF/A 4736 ( Figure 5H View FIGURE 5 ) is a left m3 with a relatively triangular-shaped outline owing to its strong distal tapering. The anterior portion is slightly eroded, but the remnants of a labial anteroconid is present on the remaining anterior cingulum. The protoconid and the metaconid are strongly connected. The protoconid is distally positioned compared to the metaconid. The hypoconid is connected to the entoconid to form the distal cusp row, and like the anterior chevron, the buccal cusp (hypconid) is slightly distal to the lingual cusp (entoconid). There is no buccal or posterior cingulum. There are no accessory cusps on the tooth and it has two roots.
Comparison and Remarks. The Dunera murine M1 and m1 differ from those of Antemus in the presence of a connection between the t4/enterostyle with the protocone on M1 and an asymmetrical ‘X’ shaped longitudinal connection between the first and second chevrons on m1. The Dunera m2 differs from those of Antemus in having a strong connection between the cusps, and the molars generally display gently, posteriorly inclined cusps, another more advanced feature compared to Antemus . The presence of a large anteroposteriorly compressed and elongated anterostyle (t1) on the Dunera M1 (visible on the CT scan with the matrix removed), and the small size of the Dunera specimens in general, also differs from that of typical Karnimata .
These new Dunera specimens share most features with Progonomys , including an M1 with an enterostyle connected to the protocone, posteriorly inclined cusps, a posteriorly shifted t1/anterostyle, and a well-defined posterior cingulum; an m1 with twinned anteroconids, an asymmetrical ‘X’ shaped longitudinal connection, a relatively well-developed (but worn) buccal cingulum, and accessory cusps C1 and C3 on the buccal cingulum. By looking at the angle of enterostyle and the angle of anterostyle among murines, the enterostyle angle on the present M1 is within the range of numerous murine species including pre- Progonomys and P. hussaini , but outside the range of Progonomys species that are known from ~9.2 Ma and younger horizons. The measured angle of anterostyle in the Dunera M1 is greater than Antemus chinjiensis , Progonomys debruijni , and pre- Progonomys , but is within the range of P. hussaini (see the angle measurements in Kimura et al., 2013, 2021). However, the enterostyle/t4 on M1 and M2 is weakly connected to the protocone unlike the strong connection in many species of Progonomys . If all of the described specimens belong to a single species, they are most similar to those described as Progonomys hussaini (Cheema at al., 2000) or “pre- Progonomys ” (Flynn et al., 2020). However, the m3 (WIMF/A 4736) is notable for its apparently large size, larger than all other measured Antemus , Progonomys , and Karnimata specimens in our sample ( Figure 6 View FIGURE 6 ; Appendix). Therefore, it is quite possible that more than one species is represented among the murine sample from Dunera.
The Dunera specimens differ from Progonomys morganae (Kimura et al., 2017) and Progonomys debruijni (Jacobs, 1978) in having a strong precingulum on M1 and strongly appressed anteroconids forming one lobe connected weakly to the second lobe lingually on m1. The present specimens also differ from Progonomys prasadi , a new species described by Patnaik et al. (2022) from the Late Miocene of Kutch, in its smaller size (for all teeth other than m3), having M1 with cusps weakly connected transversely, an m1 with a short posterior cingulum, and an m3 with the lack of C1. In overall size and shape, the specimens overlap with specimens assigned to species of Antemus and Progonomys , falling closest to the mean of P. hussaini or “pre- Progonomys ” in most comparisons ( Figure 6 View FIGURE 6 ; Appendix).
The known time-range of P. hussaini and “pre- Progonomys ” across sites in Pakistan spans a time period of ~11.6-10 Ma (Cheema et al., 2000; Flynn et al., 2020; Kimura et al., 2021). This time range accords well with previous paleomagnetic data from Dunera, which records normal polarity and has been correlated to the long C5n chron, ~11.06- 9.8 Ma (Cande and Kent, 1995; Sinha et al., 2005; Ogg, 2020). Currently, we assign these specimens to Progonomys cf. hussaini , given that they seem most similar to P. hussaini and yet are placed near the bottom of the C5n chron, close to ~11 Ma and ~500 thousand years earlier than the FAD for P. hussaini in Pakistan (Kimura et al., 2021). Because there is a time gap in major micromammal sites on the Potwar Plateau between ~11.1 Ma and 10.5 Ma (Kimura et al., 2021), it is quite possible that Dunera helps to fill in this gap and samples an earlier population of P. hussaini or a transitional stage between pre- Progonomys and P. hussaini . A biochronological estimate up to ~11 Ma (between ~11- 10 Ma) was previously suggested for the type series of P. hussaini from locality JAL- 101 in the Chinji Formation (Cheema et al., 2000). If the older age estimate for JAL-101 is correct, it may be coeval with Dunera and also sample the same time gap. Additional M 1 specimens could help confirm this assignment, but if confirmed, the Dunera specimens perhaps represent a new FAD for the P. hussaini lineage.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.