Anagalidae Simpson, 1931
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publication ID |
https://doi.org/ 10.4202/app.00292.2016 |
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persistent identifier |
https://treatment.plazi.org/id/03E687D4-FFF3-FFCB-FF1C-7BE2FA7B27CB |
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treatment provided by |
Felipe |
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scientific name |
Anagalidae Simpson, 1931 |
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Family Anagalidae Simpson, 1931 Anagalidae gen. et sp. indet.
Fig. 2A View Fig .
Material.—Right m 1 in a fragment of the mandible (IVPP V20825) from Wulanhuxiu, Erlian Basin, Nei Mongol ( China), horizon 4 (lower part), Irdinmanhan (middle Eocene).
Description.—The tooth shows a well-developed unilateral hypsodonty, the crown on the buccal side is about onethird higher (4.94 mm) than the crown on the lingual side (3.64 mm). The tooth stands upright and the anterior and posterior roots are straight and positioned close together. The total tooth height is 10.30 mm and the length of the crown is 4.44 mm. The trigonid and talonid are much more asymmetric than those of mimotonids, with trigonid wider (3.99 mm) than the talonid (3.48 mm). The occlusal surface is strongly worn but the trigonid and talonid are partly separate (by about 50% of the tooth width, including the depths of both the hypoflexid and the mesoflexid). The hypoflexid is shallower than the mesoflexid, which is delicately arched posteriorly and overall slightly more posterior. The trigonid is larger, oval, and with a gently concave occlusal surface; the bases of the main cusps are still discernible even in this strongly worn stage. The protoconid and metaconid are similar in size but the metaconid is much higher than the protoconid ( Fig. 2A 2 –A View Fig 4 View Fig ). The metaconid is the highest eminence on the occlusal surface, and is not quite aligned transversely with the protoconid, but rather shifted slightly posteriorly. There is no trace of a paraconid or paracristid and the anterior margin of the tooth is straight. The lingual side of the trigonid is no broader than the buccal one, indicating that the paraconid was absent or of negligible size.
The talonid is triangular, narrowing lingually towards a well-defined hypoconid that is slightly smaller than the protoconid ( Fig. 2A View Fig 1 View Fig , A 2 View Fig ). The hypoconid is located more lingually than the protoconid. The entoconid is well defined and is almost in line (transversely) with the hypoconid. Furthermore, the entoconid does not align with the metaconid which protrudes farther lingually. The posterobuccal part of the talonid is angled, which suggests the presence of a well-developed, asymmetrically positioned hypoconulid that is shifted strongly buccally.
Remarks.— Anagalidae are an endemic Asian group known mostly from the Paleocene of China. Only Anagale gobiensis (Ulan Gochu Formation, Nei Mongol) and Anagalopsis kansuensis (Baiyanghe Formation, western Gansu) are known to have survived to the late Eocene–early Oligocene ( Simpson 1931; Bohlin 1951; McKenna 1963). The molars of anagalids share some similarities with those of mimotonids and eurymylids, but differ in being larger and frequently more hypsodont, and in showing a slightly different cusp arrangement and overall geometry of the occlusal surface.
The described m1 is bigger than that of any known mimotonid, lagomorph or eurymylid. However, the tooth is closest in size to the m1 of Hsiuannania (see Hu 1993), being slightly smaller than that of Anagalopsis ( Bohlin 1951) and larger than that of Anagale ( Simpson 1931) . The talonid is narrower than the trigonid, whereas in the p4–m3 of the coeval taxa Gomphos and Mimolagus the occlusal planes of the crowns have square, symmetric outlines with wide talonids, and the cusps are generally aligned. Anagalid teeth frequently show asymmetry and lack precise cusp alignment. In both molars and premolars, the talonid is either wider (e.g., Anagale ; see Simpson 1931; McKenna 1963) or narrower (e.g., Huaiyangale , Hsiuannania , Qipania or Eosigale ; Xu 1976; Hu 1993) than the trigonid or may be shifted lingually.
The trigonid shows no trace of a paraconid or paracristid, but these features are variably present in anagalids, as in basal Glires . They may be present in all cheek teeth in reduced or normal form, but may also be absent in at least some teeth; in general, the paraconid and paracristid are much less persistent than the metaconid, and in heavily worn teeth may not be visible. The paraconid is lacking, for example, in molars of Hsiuannania . Moreover, the talonid of the described m1 is not typical of duplicidentates, being generally triangular, with an anteroposteriorly short lingual side and longer buccal side. The talonid narrows buccally in lagomorphs, but does not narrow lingually, and is roughly square in mimotonids. On the other hand, narrowing of the lingual margin of the talonid and lengthening of the buccal margin can be observed in some anagalids, such as Hsiuannania .
Although the described tooth is strongly worn, it is still markedly unilaterally hypsodont. The degree of hypsodonty in the Wulanhuxiu specimen is markedly increased in comparison with Mimolagus , and especially with Gomphos . Some Anagalidae show distinctly higher crowns than are present in most derived mimotonids, beeing comparable in this feature even to some primitive lagomorphs of modern aspect, such as Hypsimylus ( Meng and Hu 2004) . By contrast, mimotonids have poorly expressed hypsodonty (see Dashzeveg and Russell 1988).
The specimen from Wulanhuxiu resembles Hsiuannania in the overall tooth morphology and in having a high degree of hypsodonty, although Hsiuannania is known only from the late Paleocene of Anhui and Jiangxi, China ( Hu 1993).
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