Democricetodon fejfari Lindsay, 2017

Sehgal, Ramesh Kumar, Singh, Abhishek Pratap, Singh, Ningthoujam Premjit, Gilbert, Christopher C., Patel, Biren A. & Patnaik, Rajeev, 2023, First report of rodents from the Miocene Siwalik locality of Dunera, Pathankot District, Punjab, India, Palaeontologia Electronica (a 49) 26 (3), pp. 1-27 : 8-11

Democricetodon fejfari Lindsay, 2017

Figure 4

Holotype. YGSP 19321 , left dentary with m1–3.

Type locality. YGSP locality 388, Middle Miocene of Pakistan.

Referred materials. WIMF /A 4734 right M3 ( Figure 4A ), WIMF /A 4735 left M3 ( Figure 4B ), WIMF /A 4729 right m1 ( Figure 4C ); WIMF /A 4740 left m2 ( Figure 4D ).

Occurrence. Dunera locality, Punjab, India (study area); Middle Miocene Kulwanta (K2) locality, Ramnagar, India; early Late Miocene Tapar locality, Kutch, India; Middle to Late Miocene of Potwar Plateau, Pakistan.

Descriptions. WIMF /A 4734 ( Figure 4A ) and WIMF /A 4735 ( Figure 4B ) are both M3s with the mesial cusps and mesial portion of both teeth being much wider than the distal cusps due to strong distal tapering, resulting in a subtriangular occlusal outline. WIMF /A 4734 and 4735 are both broader than long with relatively straight (transversely) mesial margins. The protocone is the largest cusp, followed by the paracone, and the distal cusps are much reduced comparatively. On WIMF / A 4734, a small hypocone is present, and an even smaller metacone can possibly be observed, as well as the mesoloph. On the more worn WIMF /A 4735, the hypocone and metacone are not easily differentiated and appear to have been worn flat. No mesoloph is observable on WIMF /A 4735. The anterior arm of the protocone runs anteriorly towards the midline, connecting with the mesial cingulum near the midline, slightly to the lingual side of the tooth. Similarly, the paracone has an anteriorly directed crest that runs towards the midline of the tooth, meeting the mesial cingulum together with the anterior arm of the protocone. The posterior arm of the protocone is shorter than the anterior arm and is again directed towards the midline of the tooth, connecting distally with the hypocone. In WIMF /A 4734, the hypocone has a posterior crest/arm that connects with the distal cingulum. In WIMF /A 4735, which is more worn, the hypocone and distal cingulum appear indistinct from each other. A mesostyle, ectoloph, and ectostyle are all absent. On the lingual side of the tooth, the anterior cingulum curves posterolingually to terminate near the base of the protocone. On the buccal side of the tooth, the anterior cingulum is relatively long and curves more sharply, posterobuccally, to terminate near the anterior base of the paracone.

WIMF /A 4729 ( Figure 4C ) is a complete m1. The tooth is relatively long compared to its breadth and tapers mesially (or broadens posteriorly). The mesial border of the tooth is rounded in its outline. The specimen is worn and slightly damaged, making aspects if its morphology difficult to observe. The distal cusps (entoconid and hypoconid) appear larger than the anterior cusps (metaconid and protoconid). The lingual cusps are arranged slightly anterior to the labial cusps, resulting in a slightly offset appearance in occlusal view. The remnants of the anteroconid suggest that it was small and located near the midline on the anterior cingulum. Many of the occlusal crests and features are obscured by wear and/or damage. While the specimen appears most consistent in size and shape with D. fejfari , the occlusal details are not well-preserved.

WIMF /A 4740 ( Figure 4D ) is a relatively complete left m2. In occlusal view the tooth is longer than broad, which leads to an overall rectangular shape. The four main cusps (protoconid, hypoconid, metaconid, and entoconid) appear subequal in size, with the lingual cusps mesially offset from the buccal cusps. In other words, the metaconid is slightly mesial compared to the protoconid, and the entoconid is positioned slightly mesial compared to the hypoconid. The anterior arm of the protoconid is short and merged with the metalophid and the anterolophid near the midline. The posterior arm of the protoconid is also short and directed toward the entoconid, joining the posterior spur of the protoconid and the anterior mure near the midline. The posterior spur of the protoconid is directed lingually and terminates freely. The hypoconid anterior and posterior arms are short, the anterior one merged with posterior mure and the posterior arm merged with posterior cingulum. A short hypolophid and medium-length ectolophid are present. Mesolophid, mesostylid, and ectostylid are absent. The entolophid is directed buccally from the entoconid to join the anterior arm of the hypoconid near the midline of the tooth. The anterobuccal cingulum is high and curves posteriorly to terminate near the base of the protoconid. The anterolingual cingulum is also high, but it is very short and terminates on the anterior side of the metaconid. The tooth’s lingual shelf is slightly deeper than its labial shelf. The posterior cingulum is long and high, curves anteriorly, and partially encloses a shallow posterolingual basin.

Comparison and Remarks. The Siwalik Miocene Cricetidae are generally represented by two major taxonomic groups: Democricetodon and Megacricetodon (Fahlbusch, 1964; Lindsay, 2017). Democricetodon molars differ from Megacricetodon by sometimes possessing two lophs, i.e., thin crests that are directed buccally between the paracone and metacone in upper teeth, or two lophids, similar crests that are directed lingually between the metaconid and entoconid in lower teeth (Lindsay, 2017). All the cricetid specimens recovered from Dunera are here identified as Democricetodon by having two lophids between the metaconid and entoconid on m1 and m2, and a short mesoloph on M3.

In the Siwalik deposits of the Indian subcontinent, five species of Democricetodon are recognized: D. kohatensis Wessels et al., 1982 , D. fejfari Lindsay, 2017 , and three smaller and unnamed species ( Democricetodon sp. A ; Democricetodon sp. B-C; and Democricetodon sp. D ). Because they are found in older Siwalik deposits ~18 Ma, Lindsay (2017) suggested that the three smaller unnamed species might have evolved prior to their first recorded appearance, before the deposition of the Siwalik deposits in Pakistan. The last recorded species of Democricetodon is D. fejfari at ~8.7 Ma in the Siwalik deposits of Pakistan, and the first appearance of D. fejfari is ~13.8 Ma, which is also about the same time as the appearance of Antemus (Lindsay, 2017) . The Early Miocene species D. khani was reported from the Murree Formation of Banda Daud Shah, Chitarwata Formation, and Vihowa Formation of Pakistan (de Bruijn et al., 1981).

Compared to the known species of Democricetodon , the present m1 correlates well with the early Miocene species D. khani by having an extra transverse crest (protoconid posterior spur) between the metaconid and entoconid that is distinct from a true mesolophid, but differs from D. khani in its large size and sharp anterolophid. Among the Siwalik species of Democricetodon , the recovered m1 is very similar to D. fejfari . Recently, D. fejfari was also reported from the Middle Miocene K2 (Kulwanta) locality near Ramnagar, India (Parmar et al., 2022) and the Late Miocene of Gujarat, India (Bhandari et al., 2021; Patnaik et al., 2022). The m1 of D. fejfari is characterized by its relatively large size, small and single-cusped anteroconid, more offset lingual cusps that are mesially positioned compared to the labial cusps, lingually flexed posterior arm of the protoconid (resembling the mesolophid) directed toward the lingual margin of the tooth, and a short mesolophid (Lindsay, 2017). These features are present in the m1 described here and hence suggest assignment of WIMF /A 4729 to D. fejfari .

The present m2 is also comparable to D. fejfari and D. khani by the presence of the protoconid posterior spur (loph near the protocone), but the ectolophid on this tooth differs from that in D. khani . The m2 WIMF /A 4740 (length=1.88 and width= 1.57 mm) is also much larger in size than the m2 of D. khani (length= 1.2 mm and width= 0.98 mm reported in Lindsay and Flynn, 2016), and generally falls towards the larger size range for D. fejfari , particularly in length (Lindsay, 2017).

The Dunera M3 is similar to D. khani in possessing a subtriangular outline, a large protocone (larger than the other major cusps), and a prominent anterior cingulum ( Lindsay and Flynn, 2016). However, the Dunera M3 displays an indistinct metacone, which is typically distinct in D. khani from the early Miocene. Another distinct feature found in D. khani is the presence of two lophs (mesoloph and protocone posterior spur) in M3, whereas the Dunera M3 displays only one loph. While the protocone posterior spur is difficult to distinguish from the mesoloph in many rodent teeth, Lindsay and Flynn (2016) clarified that a loph close to the paracone should be recognized as the protocone posterior spur, and the loph close to the metacone should be recognized as the mesoloph. Because the Dunera specimen exhibits one loph that is close to the paracone, this loph represents the protocone posterior spur. Thus, the Dunera M3 is clearly distinguished from D. kohatensis , which instead displays a well-developed mesoloph, long anteroloph, and small size (Wessels et al., 1982). The present M3 closely resembles the M3 of D. fejfari (Lindsay, 2017) in its triangular outline, larger protocone, prominent anterior cingulum, and the presence of the protocone posterior spur.

When the size and shape of the Dunera specimens are compared to other described species of Democricetodon from the Siwaliks and Asia, more broadly (Cheema et al., 2000; Wessels and Reumer, 2009; Zhu-Ding, 2010; Lindsay and Flynn, 2016; Lindsay, 2017; Patnaik et al., 2022), the m1, m2, and M3 described here fall within the size range of D. fejfari but the shape of the Dunera m1 is slightly narrower than other D. feifari specimens (see Table 2). However, they are otherwise morphologically similar to D. fejfari , and we assign them to this species at this time.

Elements Mean Square root Mean length Mean width Taxon Locality (n=sample width/ of width* Age Reference (range) in mm (range) in mm size) length length

Democricetodon Tappar , m1 (n=2) 1.88 fejfari Kutch , India

1.98 1.05 1.93 Late Miocene Patnaik et al., (11- 10 Ma) 2022

Democricetodon China m1 (n=29) 1.43 1.05 suensis (1.25-1.60)

(0.90- 0.73 1.23 Early Zhu-Ding, 2010

1.15) Miocene Democricetodon sui China m1 (n=5) 1.26 (1.20-1.31)

Democricetodon Pakistan m1 (n=18) 1.89 fejfari (1.03-2.13)

Democricetodon Germany m1 (n=141) 1.30 gracilis (1.12-1.43)

Democricetodon Germany m1 (n=182) 1.67 mutulus (1.48-1.86)

Democricetodon Pakistan m1 (n=3) 1.50 kohatensis (1.40-1.60)

0.84 0.67 1.03 Early Maridet et al.,

(0.80-0.91) Miocene 2011

1.32 0.70 1.58 Middle to Lindsay, 2017 (0.96-1.56) Late Miocene

(13-8.7 Ma)

0.91 0.70 1.09 Middle Wessels and (0.78-1) Miocene (16 Ma) Reumer, 2009

1.11 0.66 1.36 Middle Wessels and (0.99-1.24) Miocene Reumer, 2009 (16 Ma)

1.17 0.78 1.32 Late Cheema et al., (1.15-1.20) Miocene 2000

(11-10 Ma)

Democricetodon Pakistan m1 (n=1) 1.42 khani

Democricetodon s p. Pakistan m1 (n=1) 2.05 B-C

Democricetodon sp. Pakistan m1 (n=1) 1.95 G

Democricetodon Dunera , m1 (n=1) 2.3 fejfari Punjab,

India

1

1.3

1.3

1.37

0.70 1.19 Early Lindsay and Miocene Flynn, 2016 (19 Ma)

0.63 1.63 Late Cheema et al., Miocene 2000

(11-10 Ma)

0.67 1.59 Late Cheema et al., Miocene 2000

(11- 10 Ma)

0.60 1.78 Late This study Miocene

(11-10 Ma) Democricetodon Tappar , m2 (n=7) 1.35 fejfari Kutch , India (1.25-1.45)

Democricetodon China m2 (n=38) 1.36 suensis (1.20-1.50)

Democricetodon Germany m2 (n=156) 1.18 gracilis (1.06-1.28)

Democricetodon Pakistan m2 (n=33) 1.65 fejfari (1.14-1.88)

Democricetodon Grmany m2 (n=217) 1.52 mutulus (1.37-1.68)

Democricetodon Pakistan m2 (n=2) 1.42 kohatensis (1.40-1.45)

1.06 0.79 1.20 Late Patnaik et al., (1.00-1.13) Miocene 2022

(11-10 Ma)

1.12 0.82 1.23 Early Zhu-Ding, 2010

(1.00-1.20) Miocene

0.98 0.83 1.08 Middle Wessels and (0.9-1.15) Miocene Reumer, 2009 (16 Ma)

1.42 0.86 1.53 Middle to Lindsay, 2017 (0.98-1.72) Late Miocene

(13-8.7 Ma)

1.24 0.82 1.37 Middle Wessels and (1.10-1.39) Miocene Reumer, 2009 (16 Ma)

1.17 0.82 1.29 Late Cheema et al., (1.15-1.20) Miocene 2000

(11-10 Ma)

Democricetodon Pakistan m2 (n=1) 1.21 khani

Democricetodon sp. Pakistan m2 (n=1) 1.7 B-C

Democricetodon sp. Pakistan m2 (n=1) 1.75 G

Democricetodon Dunera m2 (n=1) 1.88 fejfari

0.98

1.6

1.65

1.57

0.81 1.09 Early Lindsay and Miocene Flynn, 2016 (19 Ma)

0.94 1.65 Late Cheema et al., Miocene 2000

(11-10 Ma)

0.94 1.70 Late Cheema et al., Miocene 2000

(11- 10 Ma)

0.84 1.72 Late This study Miocene

(11-10 Ma) Democricetodon Germany M3 (n=80) 0.84 gracilis (0.70-0.94)

0.89 1.06 0.86 Middle Wessels and

(0.77-0.98) Miocene (16 Ma) Reumer, 2009

Figures

FIGURE 4. 3D surface models of Democricetodon fejfari in occlusal views. A) WIMF/A 4734, right M3; B) WIMF/A 4735, left M3; C) WIMF/A 4729, right m1; D) WIMF/A 4740, left m2. Note: Mesial towards the left and distal towards the right in all panels.