Laelaps macropus Cope 1868

LAELAPS

MACROPUS

Coelosaurus antiquus, Part, Leidy Cretaceous reptiles, p. 119 (Fragments of tibia, metatarsal bone and phalanges from Monmouth county, N. J.) also p. 101. Laelaps aquilunguis, part, Cope, Proc. A. N. Sci., Phil., 1866, 279.

The remains on which this species is based have been described by Leidy 1. c. without distinct determination. That it is distinct from the animal called by him Coelosaurus antiquus is very probable from the great difference in size (it is double the latter in most measurements), and from the greater expansion of the distal end of the tibia. Width head to tibia, 3 in. to 4in.; in Coelosaurus antiquus 25 lin. to 31 lin. However, until some additional portions of Coelosaurus are discovered, its character will remain unknown, and I prefer to associate the present with Laelaps until this is the case. The event may be that it pertains to neither genus.

It differs from Laelaps aquilunguis in its much smaller size (if adult) and in the relatively larger size of its phalanges, and consequently larger feet. Compare the transverse width of the distal end of the tibia and length of a penultimate phalange in each.

The proximal phalanges differ also in their greater depth proximally, and in that their inferior tubercle is expanded throughout the whole width of that extremity. The head of the tibia bears on its exterior outline a tuberosity not seen in L. aquilunguis (a in the outline, fig. 31).

A fragment of metatarsal is described by Leidy, and the distal extremity figured. It appears to have been the external one, and its condyle is directed slightly outwards. It is flattened on the inner face, indicating close contact with its fellow. The proximal portion of another appears to be the external of the other side. It is also flattened on the inner face, by an oblique plane which looks upwards and inwards, and which narrows distally. Proximally it widens as the face of a transverse dilatation of the extremity, which gives the articular end a V shape. See fig. 32a (nat. size). To this is added a infero-superior view of the same extremity one-half nat. size, and fig. 33, an exteroposterior, and fig. 34 an extero-anterior view of the distal extremity of the other.

* See Hays’ Medical Journal, Philada., March, 1868.

These indicate a more or less elongate metatarsal region and elevation of the heel above the ground.

Upper cretaceous, upper green sand bed Monmouth Co., N. J.