ADDITIONS AND COMMENTS ON THE FOSSIL BIRDS OF AGATE FOSSIL BEDS NATIONAL MONUMENT, SIOUX COUNTY, NEBRASKA ROBERT M. CHANDLER Department of Biological and Environmental Sciences Georgia College & State University, Milledgeville, GA 31061-0490 ABSTRACT—Fossils from Agate Fossil Beds National Monument in western Nebraska have been a rich source of paleontological studies for many years. Fossil bird discoveries from the Monument have been far fewer than mammals and their reports have been sporadic and scattered throughout the literature. Although less common than mammals, the paleoavifauna of the Monument is very interesting in its level of diversity, ecological indicators, and from the perspective of historical biogeography with Old and New World representatives. The paleoavifauna has representatives from at least six families in four orders. Promilio efferus is the earliest record for a kite in North INTRODUCTION America (Brodkorb, 1964:274). Wetmore (1923:504) had ten- T HAS been more than ten years since Becker tatively placed efferus in the genus Proictinia Shufeldt (1915: I (1987a:25) briefly reviewed the fossil birds of the “Agate 301) from the late Miocene [latest Clarendonian or earliest Fossil Quarries.” The specimens described herein were col- Hemphillian, Long Island local fauna, Phillips County, Kan- lected in 1908 by field crews from the University of Nebraska sas; see Steadman (1981:171) for comments on age of Long State Museum, but have never been identified or reported upon Island local fauna]. Later, Wetmore (1958:2) decided that until now. This collection includes the first record of a crane, Proictinia was more closely related to the Everglade Kite, Gruiformes, and additional specimens of the fossil hawk, Bu- Rostrhamus sociabilis, and that P. efferus was more like the teo ales Wetmore. Buteo typhoius Wetmore should be removed Old World carrion eating kites in the genus Milvus. Promilio from the list of species from Agate. efferus is equivalent in size and is similar osteologically to For historical accounts, the most comprehensive geologic species of Milvus. Wetmore (1958:3) placed efferus in the data and the best paleoenvironmental interpretation for the subfamily Milvinae, but in a new genus, Promilio, based on Monument and surrounding fossil localities are discussed in perceived differences. the works of Robert M. Hunt, Jr. (1972, 1978, 1981, 1985, 1990, and 1995) and Hunt and Skolnick (1996). Genus BUTEO Lacepede, 1799 (hawks) SYSTEMATIC PALEONTOLOGY BUTEO TYPHOIUS Wetmore, 1923 [An asterisk (*) indicates genera or species described from Holotype.—AMNH 1754, distal two-thirds of the right the Agate Fossil Beds. The classification sequence followed tarsometatarsus missing the trochlea for Digit II; from the below is that of the AOU Check-list, 6th edition. The follow- Lower Snake Creek, Olcott Formation (early Barstovian), 23 ing acronyms are used: American Museum of Natural His- miles south of Agate, Sioux Co., Nebraska. tory, Department of Vertebrate Paleontology (AMNH); Referred material.—HC 477, distal one half of the right Carnegie Museum of Natural History (CMNH); Harold J. Cook tibiotarsus, Agate Fossil Beds National Monument, Stenomylus collection (HC); Museum of Comparative Zoology (MCZ); Quarry 1.5 miles east of Carnegie Hill and University Hill Princeton University Geological Museum (PUGM) now at Yale quarries (referred by Wetmore, 1928:149). University, Peabody Museum; University of Nebraska State Discussion.—Buteo typhoius is osteologically very simi- Museum (UNSM)]. lar to its living congeners. Wetmore compared B. typhoius exclusively to the eastern Red-tailed Hawk, B. jamaicensis Order FALCONIFORMES borealis, from which it can be distinguished by subtle osteo- (hawks, eagles, falcons, and allies) logical differences and its much larger size (approximately 50 Family ACCIPITRIDAE percent; see Wetmore, 1923:485-492; 1928:149-150). (kites, hawks, eagles, and allies) None the less, because of the disparity in age of the type Subfamily ACCIPITRINAE locality of B. typhoius, which is the Lower Snake Creek, early (kites, hawks, and eagles) Barstovian, (see Becker, 1987b for the interesting history and Genus PROMILIO Wetmore 1958 insight into the age of the locality) and the age of the Monu- (extinct kite) ment, late Arikareean, I do not think B. typhoius occurs at PROMILIO EFFERUS (Wetmore) 1923 Agate. The tibiotarsus (HC 477) that Wetmore (1928:149) Holotype.—AMNH 6299, left tarsometatarsus missing referred to B. typhoius most likely belongs to the next species internal half of the shaft; Agate Fossil Beds National Monu- B. ales (Wetmore). Therefore, B. typhoius should be stricken ment, Upper Harrison (late Arikareean), Sioux Co., Nebraska. from the Monument species list. 1 2 TECHNICAL REPORT NPS/NRGRD/GRDTR-98/1 white Hawk-eagle (Spizastur melanoleucus). Spizastur *BUTEO ALES (Wetmore) 1926 melanoleucus is the smallest of the booted eagles, which are Holotype.—CMNH 1828, complete right tarsometatar- considered by Brown and Amadon (1968:22) to be “the most sus; Agate Fossil Beds National Monument, Carnegie Hill highly evolved members of the family and indeed of all birds (Quarry No. 2). of prey.” They live in dense, humid evergreen, and Referred material.—UNSM 3001, hallux; UNSM 3002, semideciduous forests in Central and South America (Blake, right humeral shaft; UNSM 3004, left ulna missing the ole- 1977; Howell and Webb, 1995). cranon; UNSM 3006, right femur, proximal end; UNSM 5782, left ulna, distal one/quarter; UNSM 5783, right tarsometatar- Order GALLIFORMES sus, distal end missing trochlea of Digit 4; UNSM 5784, left (grouse, quail, turkeys, and allies) tibiotarsus, proximal two/thirds; UNSM 5785, right tarsometa- Family CRACIDAE tarsus, distal one/quarter missing anterior half of trochlea of (curassows, guans, and chachalacas) Digit 3; UNSM 5786, left humerus, distal end missing the Genus BOREORTALIS entepicondyle. (extinct chachalacas) Discussion.—Buteo ales (Wetmore, 1926:403) was a large *Species BOREORTALIS TANTALA (Wetmore) 1933 hawk. The length of the holotype tarsometatarsus, CMNH Holotype.—HC 498, right tibiotarsus, distal end; Agate 1828, is 90.2mm with a distal width of 16.2mm. A hawk of Fossil Beds National Monument, Carnegie Hill. (This speci- this size is at the top of the size range for the eastern Red- men is now in the AMNH collections). tailed Hawk, B. jamaicensis borealis, given by Friedmann Discussion.—In the Neogene there are five species of bo- (1950:239). With the identification and referral of the UNSM real chachalacas in the genus Boreortalis Brodkorb (1964:304- fossils to B. ales, the assignment of this species to Buteo is 305). Boreortalis (Brodkorb, 1954:180) is closely related to affirmed. The ulna, UNSM 3003, may appear to be too long Ortalis, the genus of living chachalacas found in southern for this species (164.0mm), but is within reason when sexual Texas through Central America and into South America size dimorphism is taken into consideration for North Ameri- (Blake, 1977). It was Brodkorb’s impression that chachalacas can raptors (Snyder and Wiley, 1976). had a Nearctic origin and only during the Great American Measurements of selected fossils.—hallux (UNSM 3001) Biotic Interchange did they expand their range into South length of cord = 24.0mm; ulna (UNSM 3004) length missing America. Although boreal today, the chachalacas from these the olecranon = [164.0mm], proximal width = 15.2mm, dis- North American fossil localities would have been much more tal width = 11.0mm, depth of external condyle = 11.3mm, tropical to subtropical in nature. mid-shaft width/depth = 7.1/7.2mm; ulna (UNSM 5782) dis- tal width/depth of external condyle = 10.8/11.2mm; tibiotarsus Family PHASIANIDAE (UNSM 5784) width/depth across proximal articular surface (grouse, quail, and turkeys) = 13.5/17.5mm, length of fibular crest = 28.5mm, width/depth Subfamily TETRAONINAE of shaft below fibular crest = 7.9/6.9mm; tarsometatarsus (grouse) (UNSM 5785) distal width = 17.1, depth of trochlea Digit 4 = Genus PALAEALECTORIS 8.3mm, width of trochlea Digit 2 = 7.2mm; humerus (UNSM (extinct grouse) 5786) distal width missing entepicondyle = [21.0mm]. *Species PALAEALECTORIS INCERTUS Wetmore 1930 ACCIPITRIDAE indeterminate Holotype.—MCZ 2190, left humerus, proximal one/half Wetmore identified three other fossils only to family rank and distal end with part of shaft missing; Agate Fossil Beds with the following comments: HC 466, right ulna, proximal National Monument. end about the size of a caracara, Polyborus (Wetmore, Discussion.—This fossil grouse is between a Northern 1923:506); PUGM 12157, right tarsometatarsus, distal end Bobwhite, Colinus virginianus, and the Spruce Grouse, which resembles a Marsh Hawk, Circus hudsonius (Wetmore, Dendragapus canadensis, in size. Wetmore (1930:152-153) 1923:507); and CMNH 2207, large claw somewhat smaller thought it similar to the Spruce Grouse, but only distantly than a Golden Eagle, Aquila chrysaetos (Wetmore, 1926:406). related. Today, the Spruce Grouse is a member of the boreal I have not seen any of these fossils, but the right ulna (HC species community. Palaealectoris may represent an ances- 466) which is the size of a caracara should be re-examined tral grouse living in a subtropical environment before the di- with the UNSM ulnae referred to B. ales. chotomy we see today between boreal species like the Spruce Grouse and the prairie grouse like the Greater Prairie-Chicken, *Genus Palaeastur Tympanuchus cupido. *Species Palaeastur atavus Wetmore