Eopachypteryx praeterita Mayr, 2015, sp. nov.
Creators: name: Mayr, Gerald
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Aves
Accipitriformes
Cathartidae
Eopachypteryx
Eopachypteryx praeterita

description: Eopachypteryx praeterita, sp. nov.
Holotype. SMF-ME 825 (postcranial skeleton lacking the left leg; Fig. 1 A).
Diagnosis. As for genus.
Type locality and horizon. Messel near Darmstadt; early Eocene (Lenz et al. 2015).
Referred specimens. SMF-ME 2426 (skeleton lacking the left leg; Fig. 1 B); SMF-ME 11033A+B (cranial portion of skeleton on two slabs; Fig. 1 C, D).
Etymology. Derived from praeteritus (Lat.), past, in reference to the extinct status of the new species.
Measurements. See Table 1.
Description and comparisons. Although the skull is preserved in the two referred specimens, only a limited amount of osteological details can be obtained from these fossils (more skull features are visible in the tentatively referred specimen described below). The beak is relatively short, measuring less than half of the total skull length.
It appears to be wide at its base, but is only moderately deep and was probably of similar shape to the beak of some extant Cuculiformes (e.g., Coua). The size of the nostrils is not clearly discernible. The pterygoid (SMF-ME 2426) is long and rod-like, a facies articularis basipterygoidea and, hence, basipterygoid processes seem to be absent (Fig. 2 C). The processus oticus of the quadrate is mediolaterally broad and its caudal surface lacks pneumatic openings; the vallecula (“incisura”) intercapitularis is very shallow and a small tuberculum subcapitulare (“eminentia articularis”) can be discerned (SMF-ME 2426; Fig. 2 C). The processus (“condylus”) lateralis is well-developed and projecting, and a condylus caudalis is developed.
The mandible has moderately deep rami, which bear a lateral fossa in their midsection (Fig. 2 B). The symphysis mandibularis is of average length and is pitted by neurovascular foramina (SMF-ME 11033A). In SMF- ME 11033, ossified tracheal rings are preserved along the entire length of the cervical column.
The short cervical vertebrae are poorly preserved in all specimens (see, however, below concerning the referred specimen). A notarium seems to be absent.
The coracoid (Fig. 3 A–E) exhibits a distinctive morphology. The well developed and dorsoventrally wide facies articularis clavicularis is ventrally prominent and overhangs the sulcus coracoideus, which gives the extremitas omalis a hook-like outline if seen in ventral view. In dorsal view, the portion of the extremitas omalis between the facies articularis humeralis and the sulcus supracoracoideus forms a ridge, owing to the fact that the sulcus supracoracoideus is very steep. The cotyla scapularis is deeply excavated and cup-like; the area of the bone immediately medial of the cotyla is slightly raised. The processus procoracoideus is well developed. A foramen nervi supracoracoidei is absent. The extremitas sternalis is poorly preserved in all specimens.
The furcula is U-shaped, with robust scapi clavicularum and a wide extremitas sternalis (Fig. 4 E). An apophysis furculae is absent. The extremitas omalis is simple and does not exhibit a widened tip (Fig. 3 D, E). The scapula has a slightly curved corpus and a well-developed acromion with a broad and squarish tip.
Details of the sternum can only be seen in SMF-ME 11033, where three processus costales and two pairs of deep caudal incisions can be discerned. The carina sterni is rather low, and although the apex carinae appears to be cranially prominent, the poor preservation does not allow a close evaluation of its shape (these features are better visible in the sternum of the referred specimen described below).
The humerus (Fig. 3 L–P) is a robust bone with a large proximal end. The shaft is curved and the overall proportions of the bone are similar to those of, e.g., Trogoniformes, Columbiformes, and the extinct Archaeotrogonidae. The crista deltopectoralis is proximodistally short and has a convex dorsal margin and a concave caudal surface. The tuberculum dorsale is well developed. In both humeri of SMF-ME 11033B there appears to be second (dorsal) fossa pneumotricipitalis (Fig. 3 E, O). Such is, however, not preserved in SMF-ME 825 and the tentatively referred specimen described below, so that there remains a possibility that the appearance of a fossa in SMF-ME 11033 is a taphonomic artefact owing to the crushing of the humerus. The tuberculum supracondylare ventrale, on the distal end of the bone, is of subtriangular shape and proximodistally short. The condylus dorsalis is very narrow (SMF-ME 2426) and the condylus ventralis exhibits a depression on its cranial surface (Fig. 3 N). There is a low tuberculum supracondylare dorsale (SMF-ME 11033B, SMF-ME 825; Fig. 4 F). The left humeri of SMF-ME 11033 and the tentatively referred Eopachypteryx specimen described below are broken, with the ends of the bone being dislocated relative to each other. As noted previously (Mayr et al. 2004), broken limb bones are common in Messel birds and are likely to have caused the death of some of these animals.
The ulna only slightly exceeds the humerus in length, which distinguishes Eopachypteryx from the contemporaneous coraciiform Primobucconidae and most other small arboreal birds. On the proximal end of the bone, the olecranon is short. Details of the distal end are not clearly discernible (but see the tentatively referred specimen described below).
The carpometacarpus is craniocaudally narrow, with a wide distal symphysis. The strap-like os metacarpale minus broadens proximally (SMF-ME 2426, SMF-ME 11033A; Fig. 4 A–D). The processus extensorius is well developed and cranially prominent; it bears a distinct depression on its dorsal surface (Fig. 4 C). The processus pisiformis is centrally situated and the marked sulcus tendineus is positioned far caudally (Fig. 4 C, D).
The os carpi radiale (SMF-ME 11033B, SMF-ME 825; Fig. 4) has a similar shape to that of the Psittacidae or Nyctibiidae; it is clearly distinguished from the derived type found in “coraciiform” and piciform birds in that it is not as wide proximodistally and lacks a marked sulcus for the tendon of musculus extensor longus alulae (Mayr 2014). The hand section of the wing measures almost the length of the ulna. The phalanx digiti alulae, which bears a rudimentary ungual phalanx, is very long and reaches to the middle of the carpometacarpus. The phalanx proximalis digiti majoris exhibits a marked fossa ventralis and a small processus internus indicis.
The pelvis is comparatively small, but meaningful osteological details are not discernible in any of the specimens. The tibiotarsus exhibits very poorly developed cristae cnemiales and a proximodistally low trochlea cartilaginis tibialis (Fig. 4 G, H). The short tarsometatarsus is visible in plantar view in the two specimens with preserved legs, but only SMF-ME 825 allows the recognition of a few osteological details (Fig. 4 H). The hypotarsus is well-developed and mediolaterally wide and probably enclosed canals or deep sulci for the tendons of musculus flexor hallucis longus and musculus flexor digitorum longus (see Mayr in press for a survey of hypotarsus types in birds). The plantar surface of the shaft is slightly concave and a crista medianoplantaris is absent. The bone is only weakly arched on the level of the trochleae. The trochleae metatarsorum II and IV reach almost as far distally as the trochlea metatarsi III, but the shape of the trochleae is not discernible owing to their poor preservation; most of the trochlea metatarsi IV is furthermore broken.
The feet are too poorly preserved to assess the arrangement of the toes with certainty, although they appear to have been anisodactyl. The toes are notably short and the length of the third toe only slightly exceeds that of the tarsometatarsus. The hallux is likewise short and inserts far distally. The proximal three phalanges of the fourth toe are shorter than the penultimate one, and the proximal phalanx of the second toe has a wide proximal end. The claws are moderately long and deep, with poorly developed tubercula flexoria.
description: Published as part of Mayr, Gerald, 2015, Towards completion of the early Eocene aviary: A new bird group from the Messel oil shale (Aves, Eopachypterygidae, fam. nov.), pp. 252-264 in Zootaxa 4013 (2) on pages 253-258, DOI: 10.11646/zootaxa.4013.2.6, http://zenodo.org/record/235368