Kirtlingtonia catenata, Butler & Hooker, 2005
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publication ID |
https://doi.org/ 10.5281/zenodo.13618797 |
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persistent identifier |
https://treatment.plazi.org/id/03E187B9-FFD5-026B-FCBF-2C2AFB01FAAB |
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treatment provided by |
Felipe |
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scientific name |
Kirtlingtonia catenata |
| status |
sp. nov. |
Kirtlingtonia catenata sp. nov.
Figs. 1F, G View Fig , 5A–C View Fig .
Holotype: BMNH M46497 , the crown of a right upper molar, probably unerupted.
Paratype: BMNH M46579 , right upper molar with root .
Referred specimen: BMNH M46818, left upper premolar (bed 3p(iii)). All are from the Kirtlington Mammal Bed, Oxfordshire.
Derivation of name: Latin, catena, a chain, referring to the chains of minor cusps.
Distribution.—Late Bathonian, England.
Diagnosis.—As for the genus, by monotypy.
Description.—BMNH M46497, the holotype ( Figs. 1F View Fig , 5A View Fig ) is an unerupted tooth crown without roots, with the pulp cavity fully exposed basally. It measures 2.2 × 1.7 mm. The paratype ( Figs. 1G View Fig , 5B View Fig ) is a functioning tooth with a root, similar in size and crown pattern to the holotype. Comparison with Eleutherodon indicates that these are right upper molars, and because the root of the paratype is undivided they are regarded as last molars.
The holotype tooth is longer than wide, transverse mesially and convex distally. The highest cusp (here called a) stands at what is assumed to be the mesiobuccal corner of the crown; it is prismatic, pointed at the tip, with ridges on its slopes. It stands at the end of a buccal crest, which rises at mid−length to a cusp (b), followed by two minor elevations. At the distal end the crest turns lingually to join a distal cusp (c). Lingual to cusp a is a prismatic mesial cusp (d), which stands at the end of a central row of minor cusps of diminishing size. The central row curves at its distal end towards the buccal cusp b. The area between the buccal crest and the central row forms a basin, shallower than in Eleutherodon and without the fluting characteristic of that genus. On the lingual margin of the tooth, a series of small cusps of diminishing size runs mesiolingually from cusp c, and the area lingual to the central row is occupied by about 6 minor cusps or wrinkles, irregularly arranged.
BMNH M46579 , the paratype, is incomplete mesially, where the edge of the crown has broken away, including much of cusps a and d and the mesial part of the buccal and lingual margins. As preserved, it measures 2.05 × 1.7 mm. The only wear observed is in the basin, where longitudinal striations indicate the passage of an opposing cusp as far back as the ridge that connects cusp b to the central row. Wear buccal to the buccal row or lingual to the central row cannot be determined owing to breakage .
The root is 2.4 mm long. It measures in cross−section 1.2 mm mesiodistally and 0.9 mm in width. Its cross−sectional area is thus much smaller than the area of the crown, which overhangs the root especially on the buccal side.
Comparison.—The row of minor cusps lingual to the basin suggests a comparison with the middle row on Eleutherodon upper molars. In that case cusp d would be homologous with the enlarged cusp (Bx) at the mesial end of the middle row of Eleutherodon ( Fig. 2B View Fig 1 View Fig ). The enlarged distal cusp c might be compared with cusp B1 of Eleutherodon . However, in Kirtlingtonia the cusp row is diverted buccally towards cusp b, but in Eleutherodon it connects with cusp B1, though in one specimen (BMNH M46459; Kermack et al. 1998: fig. 7) it ends to the buccal side of cusp B1. There are many other differences: in Eleutherodon the cusps are less sharply pointed; the buccal cusps are more numerous, and the mesial one is not enlarged; the basin is deeper and its sides are fluted; there is a lingual groove and an enlarged lingual cusp BB.
The multituberculate M2 has been modified in adaptation to its lingual position in relation to M1, resulting in a different occlusal relation to m2. Whereas the buccal cusps of M1 occlude laterally to m1, those of M2 occlude in the median valley of m2. It appears as if the buccal cusps of M2 had jumped across the buccal cusps of m2. A more likely hypothesis is that the cusp rows of M2 are not serially homologous with those of M1; when M2 shifted lingually, the buccal cusp row was reduced, to become the anterobuccal ridge ( Hahn and Hahn 1998a). The lingual row now became the buccal row, and a new row was added on the lingual side. With this in mind, M2 of Paulchoffatiidae ( Hahn and Hahn 1998a) may be compared with the Kirtlingtonia tooth ( Fig. 5D, E View Fig ). The anterobuccal ridge is confined to the mesial half of the tooth. It is followed distally by a large cusp (B 2 in the nomenclature of Hahn and Hahn 1998a) that is frequently connected by a ridge to the more mesial part of the buccal row (B1, B0). B2 could be homologous with cusp b of Kirtlingtonia , the anterobuccal ridge with the mesial part of the buccal crest (with cusp a), and B1–B0 with the central cusp row arising from cusp d. Most paulchoffatiids have a distal cusp (usually termed L5) corresponding to cusp c. The series of lingual cusps is not represented in Kirtlingtonia , but it may be foreshadowed by the series of small cusps on the mesial side of c. If the M2/m2 occlusion is a diagnostic character of the order, Kirtlingtonia is not a multituberculate, but it illustrates the type of tooth from which the multituberculate M2 could have been derived.
Upper premolar ( Figs. 1H View Fig , 5C View Fig ).—BMNH M46818 has only about half the linear dimensions of Kirtlingtonia molars (1.1 × 0.85 mm) but the similarity of pattern indicates that either it represents a smaller species or it occupies a different position in the dentition. It is considered to be from the left side. The highest cusp (a), assumed to be mesiobuccal, is proportionately higher than cusp a of the holotype: its height is about 70% of the tooth length, compared with about 45% in the holotype. It is conical and sharply pointed. It is connected by a crest to a lower cusp (b) midway along the tooth. This is joined to a still lower distal cusp (c). Lingual to a is a mesiolingual cusp (d), which gives rise to a lingual ridge, made up of a row of minor cuspules, that turns buccally towards the buccal cusp b. The disto−lingual part of the crown is occupied by a ledge that extends from the tip of cusp c. The root is broken; from the fragment that survives, it appears to be vertical, and overhung by the crown buccally and lingually. If this tooth belongs to K. catenata , the elevation of cusp a makes it unlikely to be a posterior molar; it is provisionally identified as a semi−molariform premolar.
“Haramiyidan” molar BDUC J 562
Figs. 4B, 5F View Fig .
This tooth was collected from the Kirtlington Mammal Bed, Old Cement Works Quarry, Kirtlington, but is now missing. The following description is based on scanning electron micrographs and drawings.
Description.—BDUC J 562 is a relatively small molariform tooth, approximately square in outline (length 1.4 mm, width 1.5 mm). The single root indicates that it is a last molar, but whether upper or lower is uncertain. It is described here as a left lower molar, with a rounded distal margin and the highest cusps mesial. However, the presence of an additional marginal cusp might represent the rudiment of a third row, and the tooth might be upper. In that case, the highest cusps might be distal, as in other “haramiyidans”. For descriptive purposes the buccal and lingual cusps are referred to as b1... and l1... respectively, without implications of homology.
The tooth is unworn, but it has lost enamel from the mesial margin and part of the lingual margin. The cusps are sharply pointed, with apical angles of about 90 degrees. They are connected by crests and have radial ridges on their slopes. The highest cusp, considered to be mesiolingual (l1) is connected by a transverse crest to the first buccal cusp (b1), and it also has an oblique ridge running into the basin. There are four lingual cusps of diminishing size; at the distal end the series curves buccally to meet the end of the buccal row, closing the basin. The lingual margin next to l1 has broken off, but a small prominence lingual to l2 suggests that a cingulum may have been present there. Of the four buccal cusps, b1 and b3 are lower than l1 and similar in height to l2; b2 and b4 are small. An additional small cusp stands on the buccal margin next to b2. The basin, bounded mesially by the ridge from b1 to l1 and distally by the terminal part of the lingual cusp row, is free of ornament except for the ridges on the cusps. It is shallowly concave, deepest between l2 and b3. The root is 2 mm long, and slightly curved mesially. Transversely it measures 1.0 × 1.15 mm, thus much less than the crown.
Comparison.—This tooth shows some resemblance to Thomasia , especially the shorter posterior upper molars called Haramiya I bis by Sigogneau−Russell (1989): the distal cusps connected by a transverse ridge (“saddle”), and closure of the basin by union of the cusp rows (“U−ridge”). However, the cusps of Thomasia are more rounded, and they do not have radial ridges. There is more resemblance in this respect to Kirtlingtonia , with which BDUC J 562 also agrees in the relatively small cross−sectional area of the root. It is somewhat narrower than M2 of Kirtlingtonia but much shorter, and occlusion between the teeth seems unlikely. Interpretation of J 562 must await the discovery of further material; at present it can only be classified incertae sedis.
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