Paralbula sp.

Ostrowski, Summer A., 2021, Late Cretaceous Elopomorpha (Actinopterygii: Teleostei) from the Mahajanga Basin of Madagascar and impacts on paleobiogeography, Palaeontologia Electronica (a 31) 24 (3), pp. 1-15 : 6

Paralbula sp.

Figure 4

Material. Three tooth plates ( DMNH EPV.136304, UA 11391, and UA 11392).

Occurrence. Berivotra Study Area (Anembalemba Member) and Lac Kinkony Study Area (Lac Kinkony Member).

Description. Tooth plate DMNH EPV.136304 ( Figure 4 A-B) measures 1.4 cm long, 0.8 cm wide, and ranges in thickness from 0.1-0.3 cm. Lateral view of the tooth plate exhibits three to four layers of hemispherical teeth with irregular (offset, non-vertical) stacking. Individual teeth are 0.5-1.0 mm wide at the crown. No bony base is present. Tooth plate UA 11391 ( Figure 4 C-D) is incomplete with uneven margins and measures 1.1 cm long, 0.9 cm wide, and 0.25 cm thick. The thickness is relatively uniform with a slight undulating surface. The teeth are arranged in three or four layers with irregular stacking. Individual teeth are hemispherical with thick enamel exhibiting a punctate surface texture and are uniform at 1 mm in crown width. Tooth plate UA 11392 ( Figure 4 E-F) measures 1.2 cm long, 0.6 cm wide, and ranges in thickness from 0.2-0.4 cm. The overall surface of the tooth plate is not smooth and shows undulations. From a lateral view of the tooth plate, the teeth are arranged in two to three layers with irregular stacking. Individual teeth range from 1-2 mm in width across the crown; many have broken enamel, and a punctate surface texture. Very little, poorly preserved bony base is present.

Remarks. Paralbula tooth plates are identified on the basis of the following criteria: 1) alternate tooth placement; 2) hemispherical teeth with a basilar foramen; 3) tooth surface is smooth or sparsely punctate (can occur radially); and 4) tooth plate with a curved occlusal surface ( Estes, 1969). The tooth plates described here exhibit domed occlusal surfaces that are slightly flattened anatomically, not from deformation. Individual teeth have relatively smooth surface textures, and are hemispherical or slightly flattened, irregular to slightly elongate, with thick enamel. The individual teeth are strongly cemented together, and several of the teeth are weathered on the occlusal surfaces. These tooth plates identified as Paralbula occur mostly within the Lac Kinkony Member but have been found in the Anembalemba Member. The holotype specimen of Paralbula marylandica , from the Eocene of Maryland ( Blake, 1940), possesses the four features listed above and is directly comparable to the Paralbula tooth plates from Madagascar.

Figures

FIGURE 4. Paralbula sp. fossils from the Maevarano Formation. A-B occlusal and lateral views of tooth plate (DMNH EPV.136304). C-D occlusal and lateral views of tooth plate (UA 11391). E-F, occlusal and lateral views of tooth plate (UA 11392). Scale bar equals 1 cm.