Part 9

Because the specimens treated here are avian and of Mesozoic age, it is almost certain that too much importance will be made of them by some future authors. Indeed, it will probably be years before the literature can be expunged of the records of presumed occurrences that arose from previous misidentifications of these fossils. Therefore, in an effort to forestall overenthusiasm for these fragments we shall present our own brief assessment of their significance.

Unlike most other Cretaceous birds, such as the Hesperornithiformes, Ichthyornithiformes, and Enantiornithiformes, which represent totally extinct lineages (Olson, 1985), the Cretaceous birds of New Jersey are of essentially modern aspect. However, there are no modern families of birds represented in the fauna. The differences among the fossils suggest that at least two orders are represented, but whether any or all of the species can be placed in modern orders is more difficult to say. This stems as much from the unsatisfactory state of the ordinal classification of modern birds (Olson, 1981, 1985), as from the incompleteness of the fossils. There are certain modern birds, for example the Burhinidae, with sufficient similarities to some of the Cretaceous fossils that there would be no problem with associating them in the same ordinal-level taxon, though it would be more difficult to say which other modern families should also be included.

The material is too poor to state how many families are represented in the fauna, although if the various members of the “form-family” Graculavidae were better known there can scarcely be any doubt that more than one family would be recognized in this group. Within the Graculavidae from New Jersey there appear to be six genera (Graculavus, Telmatornis, Palaeotringa, Laornis, Anatalavis, and an unnamed genus). These are diverse, ranging in size from the smallest of the modern Burhinidae to that of a large crane. The very short, robust, curved humeri of Anatalavis indicate some diversity in mode of flight as well. The greatest similarity of most of these forms is to the early Paleogene bird Presbyornis, and then to the modern family Burhinidae. Because these two groups are very different in their habits and feeding adaptations we may expect that the various members of the Graculavidae were probably as divergent from one another as are Presbyornis and Burhinus, their similarities being almost certainly due to the retention of primitive characters.

Including the two genera and species that show some similarities to the Procellariiformes, along with the small indeterminate femur, the total avifauna from the New Jersey greensands comprises 8 or 9 genera and 9 or 10 species. As far as can be determined, all of the birds in this assemblage were probably marine or littoral in habits. We certainly would not interpret this as indicating that waterbirds are primitive and that they gave rise to land birds, as suggested by Thulborn and Hamley (1985) in their fantastic and highly improbable conjectures as to the mode of life of Archaeopteryx. Indeed, just the opposite is probably the case (Olson, 1985), the lack of Late Cretaceous fossils of truly terrestrial or arboreal birds most likely being due to sampling bias.

Appendix

The nonavian megafauna of the main fossiliferous layer (Basal Hornerstown Formation), at the Inversand Company marl pit, Sewell, Gloucester County, New Jersey is listed below. Also found in the deposits were numerous coprolites of sharks and crocodilians, some amber, phosphatized wood, and a few seeds. Voucher specimens are in the collections of the New Jersey State Museum, Academy of Natural Sciences of Philadelphia, and Yale University (Princeton University collections).

Brachiopoda

Terebratulina atlantica (Morton)

Gastropoda

Gyrodes abyssinus (Morton) Acteon cretacea Gabb Anchura abrupta Conrad Turbinella parva Gabb Lunatia halli Gabb Pyropsis trochiformis (Tuomey) Volutoderma ovata Whitfield Turbinella subconica Gabb Turritella vertebroides Morton

Pelecypoda

Cardium tenuistriatum Whitfield Glycymeris mortoni (Conrad) Gryphaea convexa (Say) Gervilliopsis ensiformis (Conrad) Panopea decisa Conrad Veniella conradi Morton Crassatella vadosa Morton Cucullaea vulgaris Morton Lithophaga ripleyana Gabb Xylophagella irregularis (Gabb) Nuculana stephensoni Richards Etea delawarensis (Gabb)

Nautiloidea

Eutrephoceras dekayi (Morton)

Ammonoidea

Baculites ovatus Say Sphenodiscus lobatus (Tuomey) Pachydiscus (Neodesmoceras) sp.

Crustacea

cf. Hoploparia sp.

Chondrichthyes

Lamma appendiculata (Agassiz) Odontaspis cuspidata (Agassiz) Squalicorax pristodontus (Morton) Hexanchus sp. Edaphodon stenobryus (Cope) Edaphodon mirificus Leidy Ischyodus cf. I. thurmanni Pictet and Campiche Squatina sp. Myliobatis cf. M. leidyi Hay Ischyrhiza mira Leidy Rhinoptera sp. cf. Rhombodus levis Cappetta and Case

Osteichthyes

Enchodus cf. E. ferox Leidy Enchodus cf. E. serrulalus Fowler Paralbula casei Estes

Chelonia

Adocus beatus Leidy Osteopygis emarginatus Cope Taphrospys sulcatus (Leidy) Dollochelys atlantica (Zangerl)

Crocodilia

cf. Procaimanoidea sp. Hyposaurus rogersii Owen Thoracosaurus sp. Bottosaurus harlani Meyer Diplocynodon sp.

Lacertilia

Mosasaurus sp. Plioplatecarpus sp.