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Home , Austin Chalk, Bird, Graculavus, Ichthyornis

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DAVID C. PARRIS AND JOAN ECHOLS Bureau of , New Jersey State Museum, CN-530, Trenton, New Jersey 08625-0530, and Department oj Sciences, East Texas State University, Commerce, Texas 75428

ABSTRACT.—Four avian from the Cretaceous of Texas are referred to Ichthyornis. Two specimens identified as /. dispar (Marsh, 1872) are from the Ector Chalk () of Fannin County. One specimen referred to /. antecessor (Wetmore, 1962) is from the Pflugerville Formation of Travis County, and another is from the Roxton Member of the Gober Chalk of Fannin County, both . The Texas specimens can be correlated with greater precision than most material of Ichthyornis and span a period essentially equal to that during which the , source of the classic specimens, was deposited. Key words: Ichthyornis; Cretaceous; ; geology; bird.

Since it was first described, the avian Ichthyornis has been among the taxa most associated with the classic chalk strata of . The six described by Marsh (summarized in Marsh, 1880) from the Niobrara Formation (Coniacian-Campanian) established Ichthyornis as one of the notable toothed of the Cretaceous of , a genus familiar to anyone with a basic knowledge of paleontology. Interest in Ichthyornis has increased in the last few decades (Walker, 1967; Stewart, 1990; Stewart et al., 1990). Descriptions of better specimens than those available to Marsh have reinforced knowledge of the of the genus (Gingerich, 1972; Martin and Stewart, 1977). The geologic and geographic ranges have been greatly expanded in other published reports (Olson, 1975; Lucas and Sullivan, 1982; Martin and Stewart, 1982; Fox, 1984; Zinsmeister, 1985; Nesov, 1986). As yet, however, no comprehensive taxonomic review of the genus has been published, although such a study is much to be desired. Ichthyornis was reported from the Cretaceous of Texas by Marsh (1877). The Yale University specimen (YPM 1796), the only published report of an alleged Cretaceous bird from Texas, was designated the type of a distinct species, Ichthyornis lentus (originally referred to the genus ). The specimen was attributed to the Austin Chalk near Fort McKinney (now McKinney), Collin County (misprinted as Colling County in Brodkorb, 1967). The taxonomic identity and geologic age of that specimen have been questioned, however (Shufeldt, 1915; Martin and Stewart, 1982). Despite skepticism about /. lentus, the genus Ichthyornis would be expected to occur in the chalk horizons of Texas. In fact, two well-documented Texas specimens of Ichthyornis have been known since 1940, although they apparently have not been described. Their existence presumably was noted in organizational reports 202 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

and they were studied by leading authorities on the genus. Unfortunately, reviewers of Cretaceous (Russell, 1988) generally were unaware of these specimens. We describe here four Texas specimens of Ichthyornis, the two noted above and two that have been collected more recently. All are from the Austin Division of Young (1986), a single transgression-inundation event (Fig. 1). Texas specimens of Ichthyornis are of particular importance because of their intermediate geographic position between records from Kansas and , and because the well-studied biostratigraphy of Texas (especially ammonite zonation) enables a high degree of age resolution for them. Institutional collection prefixes used here are: ET, East Texas State University; TMM, Texas Memorial Museum; USNM, National Museum of Natural History (Smithsonian Institution); YPM, Yale University (Peabody Museum of Natural History).

SYSTEMATIC PALEONTOLOGY Ichthyornithiformes Marsh, 1873 Family Ichthyornithidae Marsh, 1873 Genus Ichthyornis Marsh, 1872 Ichthyornis dispar (Marsh, 1872)

Holotype.—YPM 1450, an incomplete postcranial skeleton from the Smoky Hill Chalk Member of the Niobrara Formation in Section 1, Township 6 S, Range 19 W, Rooks Co., Kansas. Referred specimens.—TMM 31051-24, a complete right humerus (Fig. 2), and TMM 31051-25, a right with complete humerus, partial ulna, partial radius, and portion of (Fig. 3), both specimens from the Ector Chalk Formation of the Austin Group at the Savoy Pit, Fannin Co., Texas (Ector 7.5' Quadrangle). For descriptions of the locality and Bureau of Economic Geology collecting projects, refer to Springer (1957) and Bardack (1968). Collected by Bureau of Economic Geology field party (Gregory) in 1940. Description.—The specimens are well preserved except for minor breakage and crushing, and include the conspicuous pectoral crests of the humerus that are diagnostic of the genus. Pending a generic revision, the best means of species determination remains comparison of measure­ ments to specimens described by Marsh himself. As shown in Table 1, the TMM humeri are similar to the Marsh specimens of Ichthyornis dispar, including the type. Other species of the genus for which the humerus is known differ significantly in dimensions. Both of the referred specimens from Texas are prepared in relief on blocks of matrix, somewhat limiting the views available for detailed description. However, the shaft is ICHTHYORNIS FROM THE CRETACEOUS OF TEXAS 203

FIGURE 1. Part of northeastern Texas with primary outcrop area of Austin Group (after Oetking, 1959). Localities of specimens are Gober (G) and Savoy (S) in Fannin County, and Austin (A) in Travis County. Inset shows relationships of Austin Division rocks (after Young, 1986). relatively robust in both of the distal ends of the humeri, a characteristic of /. dispar noted by Olson (1975). Length of the ulna as preserved is 63.5 mm. Discussion.—Although a revision of the genus probably will result in a reduction in the number of species of Ichthyornis, the validity of the 204 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

FIGURE 2 (upper). TMM 31051-24, Ichthyornis dispar, right humerus, oblique view of anconal side. FIGURE 3. TMM 31051-25, Ichthyornis dispar, semiarticulated partial right wing, oblique view of distorted humerus.

species /. dispar likely will be sustained. Although it was the second species of Ichthyornis to be described, it was the first to be directly attributed to the genus, and is, therefore, considered the type species (Brodkorb, 1967). It is certainly the most appropriate name in this case, because the type specimen is adequate for diagnosis and includes skeletal elements that are directly comparable. The type of /. anceps (the only species of Ichthyornis described prior to /. dispar) is too fragmentary to be useful for most specific diagnoses, being merely the distal end of a ICHTHYORNIS FROM THE CRETACEOUS OF TEXAS 205

TABLE 1. Measurements of Ichthyornis humeri (mm).

/. dispar /. dispar YPM 1450 YPM 1730 TMM 31051-24 TMM 31051-25 Length 58.0 62.5 63.8 62.5 Greatest proximal diameter 13.0 15. - - Distal width 9.6 9. 9.6 8.2 Humerus distal depth 5.0 - - - Ulnar condyle diameter - 5. 4.6 5.2 Measurements of YPM specimens published by Marsh (1880). carpometarcarpus. However, it seems distinct from /. dispar based on size, as noted by Marsh (1880), who published dimensions of the types. Stratigraphy.—The Ector Chalk is the formation of the Austin Group and is the lowest unit of the Austin Division in the lithogenetic classification of Young (1986). It is within the Peroniceras haasi Zone of Young (1963) and correlates with the lower Coniacian Stage. The type specimen of Ichthyornis dispar is from Rooks County, Kansas, from a locality mapped in the combined zones of Cladoceramus undulatoplicatus and Platyceramus platinus by Stewart (1988),—his Protosphyraena Zone D. Thus it probably correlates with the Stage.

Ichthyornis antecessor (Wetmore, 1962) Holotype.—USNM 22820, the distal end of left humerus from the Mooreville Formation (Selma Group) at Hewletts Farm, Greene Co., Alabama. Referred specimens.—TMM 42522-1 (Figs. 4 and 5), distal end of left humerus from the Pflugerville Formation at the Little Walnut Creek-Old Sprinkle Bridge Locality in Austin, Travis Co., Texas (Austin East 7.5' Quadrangle). For description of the locality, see Young (1977). Obtained by A. Busbey in 1985. ET 4396 (L85-6), the proximal end of a left carpometacarpus (Figs. 6- 8), from the Roxton Limestone Member of the Gober Formation at East Texas State Locality 36, "Dig 2," obtained by D. Galbraith, J. Echols, G. T. James, C. L. Rowett, and their East Texas State University earth science class in the spring of 1965. The horizon was the upper Roxton Limestone Member, about 15 centimeters below the top of the Gober Chalk Formation, on the Woodson property approximately 100 meters upstream from a bridge on an unnamed and unnumbered county road, approximately one kilometer due east of Gober, Fannin Co., Texas, on an unnamed tributary of the North Sulphur River (Gober 7.5' Quadrangle). Description.—TMM 42522-1 is directly comparable to the type of /. 206 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

FIGURE 4 (upper). TMM 42522-1, Ichthyornis antecessor, distal left humerus, palmar view. FIGURE 5. TMM 42522-1, Ichthyornis antecessor, distal left humerus, anconal view. antecessor and is only slightly smaller (distal diameter 10.1 mm, ulnar condyle diameter 5.7 mm). The shaft is slenderer than in /. dispar, as noted by Olson (1975), a feature clearly observable although only a small portion of the shaft is preserved. The configuration of the brachial depression resembles that of the type specimen as illustrated by Olson (1975), and the ectepicondylar process is similarly placed. As these features were designated as distinctive of the type, there seems to be no doubt that the Austin, Texas, specimen is /. antecessor. Review of the ICHTHYORNIS FROM THE CRETACEOUS OF TEXAS 207 genus could demonstrate that /. antecessor is a junior of a previously described species, however. No specimens other than humeri can be compared directly to the type of /. antecessor; however, the carpometacarpus, of ET 4396 (L85-6), reasonably may be attributed to that species. It seems distinct from other species of Ichthyornis for which the carpometacarpus is known, as discussed below. It is of approximately the same geologic age as both the type of /. antecessor and the distal humerus referred to above, and is later in geologic age than all other known species. Identification of the carpometacarpus as Ichthyornis is based on the shape of the trochlea of the proximal end. In end view, the grooved aspect of the carpal trochlea is poorly developed, whereas it is well- developed in birds generally. The shape in end view is somewhat rectangular, excepting the metacarpal I process, with the width being about two-thirds of the length. This aspect differs from the condition in all other orders of birds and was noted by Marsh as distinctive of Ichthyornis. He described it (Marsh, 1880) as an articulation that was "plane transversely and oblique throughout with only one curvature" and "destitute of the groove ordinarily seen at the ulnar side of this articulation." Identification of this specimen as Ichthyornis also is supported by several other characteristics. The process of metacarpal I is of moderate size, as in most birds. Its most distal extent is approximately the same as the divergence of metacarpal III from the opposite side of the fused . This is the condition expected for Ichthyornis, as described by Marsh (1880). In most avian orders, the divergence of metacarpal III begins at a more distal position, although there are similar conditions in some . The precise shape of metacarpal I in ET 4396 (L85-6) is a process of uniform width with its exterior edge slightly curved back proximad (although it is broken and difficult to describe fully). There is no evidence of a protuberance at the distal end of metacarpal I (which also is slightly damaged). It is identical to the condition in Ichthyornis so far as may be observed in this specimen. We have compared ET 4396 (L85-6) to six carpometacarpi of Ichthyornis from classic Kansas localities. Although some specimens are crushed or broken, or both, there are some features that seem consistent among them and that distinguish them from ET 4396 (L85-6). The carpal trochlear surface in internal view is essentially not visible in typical Niobrara specimens regardless of species. In ET 4396 (L85-6), the trochlear surface projects slightly more proximad and is oriented somewhat obliquely so that it is visible in internal view. The exterior corner of metacarpal I is upturned proximad more closely to metacarpal 208 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

FIGURE 6 (upper). ET 4396 (L85-6), Ichthyornis antecessor, proximal left carpometacarpus, internal view. FIGURE 7. ET 4396 (L85-6), Ichthyornis antecessor, proximal left carpometacarpus, external view. ICHTHYORNIS FROM THE CRETACEOUS OF TEXAS 209

FIGURE 8. ET 4396 (L85-6), Ichthyornis antecessor, proximal left carpometacarpus: A, end view (left); B, internal view (center); C, external view (right).

II in ET 4396 (L85-6) than in any Niobrara specimen; indeed, some of the processes in Niobrara specimens are upturned only slightly. The proximal portion of metacarpal III is more prominent in the Kansas Niobrara specimens than it is in ET 4396 (L85-6). The overall aspect thus observed is of a more gracile appearance for ET 4396 (L85-6) relative to any Niobrara specimen, although the damage to metacarpal I in the Texas specimen tends to exaggerate that appearance. The distinctive aspects of ET 4396 (L85-6) suggest that is a different species from any Niobrara specimen, and that it can be attributed tentatively to /. antecessor. More gracile proportions in /. antecessor than in other species of Ichthyornis would seem to be consistent with the more slender shaft of the holotypical humerus. Stratigraphy.—TMM 42522-1 is from a well-known locality for which correlations are thoroughly established (Young, 1977). The Pflugerville Formation of the Austin Group is within the Delawarella delawarensis Zone and correlates with the Lower Campanian Substage (Young, 1986). ET 4396 (L85-6) is from the Gober Formation (specifically the Roxton Limestone), which is the same age as the Pflugerville Formation (Young, 1963, 1986; Beikirch and Feldman, 1980), being within the same ammonite zone. Both formations are within the Austin Division of Young (1986). The type specimen of /. antecessor, following the discussions of Young (1963), Owens et al. (1970), and Martin and Stewart 210 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

(1982), should be of essentially the same age as the two Texas specimens or possibly slightly younger. The Roxton Limestone Member of the Gober Formation is not yet recognized fully by the United States Geological Survey, but has general acceptance among Texas geologists (Echols, 1972). Although a complete taphonomic analysis has not been attempted as yet for this vertebrate- bearing unit, some of the more interesting aspects are worthy of reiteration here for comparison with other Ichthyornis sites. The Roxton Limestone is unusual among carbonates, being a fragmental glauconitic biomicrite with large fragments (indicative of a high energy environment) within a micritic matrix (typical of a low energy situation). The Roxton Member has been compared to classic condensed units. Echols (1972) noted evidence of enrichment by winnowing, cessation of sedimentation, and washing together of scattered material by water movements, as well as bioturbation as possible causes of the fossil concentration. The evidence for low energy environment of deposition is consistent with other marine Cretaceous units that have yielded fossil birds, notably those with glauconite and chalk components (Olson and Parris, 1987).

IMPORTANCE OF TEXAS ICHTHYORNIS SPECIMENS As previously noted, Ichthyornis specimens from Texas all are attributable to formations of the Austin Division of Young (1986), a division being Young's term for formations related by a single transgression-inundation event. These Texas specimens can be related to ammonite-zoned biostratigraphy better than any other known materials of the genus. The four Texas specimens, two from each of two chronostratigraphic horizons, cover a time span (early Coniacian-early Campanian) that is essentially equivalent to that of the entire Niobrara Formation, the classic source of Ichthyornis. A much-needed revision of the genus may well be dependent on such materials, which are more reliably correlated in worldwide sequences than any others of the genus. More Ichthyornis material should be sought in Texas, and the many fine amateur collections there should be examined for undetected specimens.

ACKNOWLEDGMENTS We thank Barbara Smith Grandstaff, Dr. J. D. Stewart, and Dr. W. J. Zinsmeister for useful information and comments. Dr. and Ms. Mary Ann Turner provided access and loans to the collections of the Yale Peabody Museum. Dr. Melissa Winans furnished information and loans from the collections of the University of Texas at Austin. Dr. Arthur Busbey was especially helpful, providing extensive information on the locality of TMM 42522-1, the specimen which he collected. Drs. William B. Gallagher, Storrs Olson, Robert Ramsdell, and Daniel Womochel kindly read and commented on the manuscript. The technical drawings were produced by Ms. Betty Montgomery of , Texas. ICHTHYORNIS FROM THE CRETACEOUS OF TEXAS 211

Photographs were taken by Barbara Smith Grandstaff and Dr. Wayne L. Parris for the New Jersey State Museum.

LITERATURE CITED Bardack, D. 1968. Belonostomus sp., the first holostean from the Austin Chalk (Cretaceous) of Texas. J. Paleontol., 42:1307-1309. Beikirch, D. W. and R. M. Feldmann. 1980. Decapod crustaceans from the Pflugerville Member, Austin Formation (: Campanian) of Texas. J. Paleontol., 54:309-324. Brodkorb, P. 1967. Catalogue of fossil birds: part 3 (Ralliformes, Ichthyornithiformes, Charadriiformes). Bull. Florida State Mus., 2:99-220. Echols, J. 1972. Biostratigraphy and faunas of the upper Austin and Taylor groups (Upper Cretaceous) of Texas, with special reference to Hunt, Fannin, Lamar, and Delta counties, Texas. Unpublished Ph.D. dissertation, Univ. Oklahoma, Norman, 244 pp. Fox, R. C. 1984. Ichthyornis (Aves) from the early (late Cretaceous) of Alberta. Canadian J. Earth Sci., 22:258-260. Gingerich, P. D. 1972. A new partial mandible of Ichthyornis. , 74:471-473. Lucas, S. G., and R. M. Sullivan. 1982. Ichthyornis in the Late Cretaceous Mancos Shale (Juana Lopez Member), Northwestern New Mexico. J. Paleontol., 56:545-547. Marsh, O. C. 1877. New vertebrate fossils. Amer. J. Sci. (3) xiv: 249-256. . 1880. : a monograph on the extinct toothed birds of North America. Rept. U.S. Geol. Exploration of the Fortieth Parallel, 7: xv + 1-201. Martin, L. D., and J. D. Stewart. 1977. Teeth in Ichthyornis (class Aves). Science, 195:1331-1337. . 1982. An ichthyornithiform bird from the Campanian of Canada. Canadian J. Earth Sci., 19:324-327. Nesov, L. 1986. Pervaya nakhodka pozdnemelovoy ptitsyikhtiornisa v starom svete i nekotoryye drugiye kosti ptits iz mela i paleogena Sredney Axii [The first find of the late Cretaceous bird, Ichthyornis, in the Old World, and some other bird from the Cretaceous and of Middle Asia]. Ekologicheskiye i faunisticheskiye issledovniya ptits (Potapov, Roal'd Leonidovich ed.), Tr. Zool. Inst. Akad. Nauk SSR, 147:31-38. Oetking, P. F. 1959. Geologic highway map of Texas. Dallas Geol. Soc. (map). Olson, S. L. 1975. Ichthyornis in the late Cretaceous of Alabama. Wilson Bull., 87:103-105. Olson, S. L., and D. C. Parris. 1987. The Cretaceous birds of New Jersey. Smithsonian Contrib. Paleobiol., 63:1-22. Owens, J. P., J. P. Minard, N. F. Sohl, and J. F. Mello. 1970. Stratigraphy of the outcropping post-Magothy Upper Cretaceous formations in southern New Jersey and northern Delmarva Peninsula, Delaware and Maryland. U. S. Geol. Surv. Prof. Paper, 674:1-60. Russell, D. A. 1988. A checklist of North American marine Cretaceous including fresh water . Occas. Papers Tyrrell Mus. Palaeontol., 4:1-58. Shufeldt, R. W. 1915. Fossil birds in the Marsh Collection of Yale University. Trans. Connecticut Acad. Arts Sci., 19:1-110. Springer, V. G. 1957. A new genus and species of elopid (Laminospondylus transversus) from the Upper Cretaceous of Texas. Copeia, 1957: 135-140. Stewart J. D. 1988. The stratigraphic distribution of late Cretaceous Protosphyraena in Kansas and Alabama. Fort Hays Studies., 3rd sen, 10:80-94. . 1990. Stratigraphic distribution of Niobrara vertebrates. Pp. 19-30, in Niobrara Chalk Excursion Guidebook, Soc. Vert. Paleo., 50th anniversary meeting at Lawrence, Kansas. 212 THE TEXAS JOURNAL OF SCIENCE—VOL. 44, NO. 2, 1992

Stewart, J. D., S. C. Bennett, and R. J. Zakrzeski 1990. Road log from Lawrence to the type area of the Niobrara Chalk. Pp. 3-12, in Niobrara Chalk Excursion Guidebook, Soc. Vert. Paleo., 50th anniversary meeting at Lawrence, Kansas. Walker, M. V. 1967. Revival of interest in the toothed birds of Kansas. Trans. Kansas Acad. Sci., 70:60-66. Young, K. 1963. Upper Cretaceous ammonites from the Gulf Coast of the United States. Publ. Univ. Texas Bur. Econ. Geol., 6304: viii + 1-373. . 1977. Rocks of the Austin area. Pp. 16-75, in Guidebook to the geology of Travis County (K. Young, ed.). Univ. Texas, Student Geol. Soc, 7:16-75. . 1986. Cretaceous marine inundations of the San Marcos Platform, Texas. Cret. Research, 7:117-140. Zinsmeister, W. J. 1985. 1985 Seymour Island expedition. Antarctic J. U.S., 20:41-42. THE TEXAS ACADEMY OF SCIENCE, 1992-93

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