DISCOVERY OP THE TITANOTHERES AND ORIGINAL DESCRIPTIONS 



209 



Type. — Fractured horns and nasals. The present 

 location of this type has not been determined. It is 

 not in the collection of the Philadelphia Academy, 

 nor is any record of its loan to be found. (See fig. 

 164.) 



Characters of type. — Leidy's description is too long 

 to quote here. The specimen may be described briefly 

 as follows: Seen from above the nasals are of moderate 

 length and taper toward the extremities; from the 

 side and front they appear decidedly long and thin 

 and are strongly decurved at the tip, at which point 

 there is a median notch. The horns project forward 

 and outward and pass from an elongate oval section 

 at the base to rounded, transversely oval tips. The 

 greatest diameter of the horns at the base is antero- 

 posterior, with flattened outer and convex inner 

 faces. The following approximate measurements are 

 taken from Leidy's descriptions and figures: 



Millimeters 



Free width of nasals 108 



Free length 104 



Outside measurement of horns 140 



Etymology. — coloradensis , in allusion to the type 

 locality. 



Present determination. — The type of Megacerops 

 coloradensis, consisting of the osseous horns and nasals, 

 is apparently distinct specifically from Cope's M. acer, 

 M. hucco. 



SPECIES DESCRIBED BY MARSH AND COPE IN 1873-1876 

 Brontotherium Marsh, 1873 



Cf. Brontotherium, this monograph, pages 555-557 



Original reference. — Am. Jour. Sci., 3d ser., vol. 5, 

 p. 486, 1873 (Marsh, 1873.1). 



Type species. — Brontotherium gigas Marsh. (See 

 below.) 



Generic characters. — Marsh writes: 



An examination of the remains, in the Yale Museum, of the 

 huge mammals allied to Titanotherium has led to the discovery 

 that two different animals have hitherto been referred to the 

 species known as T. prouti. These animals are generically dis- 

 tinct and probably are from separate geological horizons. 

 The one here described differs from Titanotherium in its denti- 

 tion, having but three lower premolars, the series being as fol- 

 lows: Incisors 2, canine 1, premolars 3, molars 3. The animal 

 was, moreover, a true perissodactyl, with limb bones resembling 

 those of Rhinoceros. The genus is related to Titanotherium, and 

 the two appear to form a distinct family, which may be called 

 Brontotheridae. The present species is based on portions of 

 three individuals, one of which has the lower jaws and en- 

 tire molar series complete. They indicate an animal fully 

 equal to T. prouti in size, and but little inferior in bulk to the 

 elephant. The lower molars resemble those in the type speci- 

 men of T. prouti, but the jaw below them is not so deep, and its 

 lower margin is more nearly straight, descending but very 

 slightly toward the angle. The front part of the lower jaws is 

 somewhat suilline in form. The incisors are quite small, and 

 the two next to the symphysis are separated from each other. 

 There is a short diastema between the canine and the first 

 premolar. [This is followed by remarks on the skeleton based 

 on the "other specimens."] 



Etymology: fipovTi], thunder; drjpiov, beast. 



Present determination. — This was the most impor- 

 tant contribution to the knowledge of the titanotheres 

 made up to that time. The characters of the lower 

 jaw and of the skeleton are correctly described, and the 

 family is referred to the Perissodactyla. Subsequent 

 research has shown that the genus Brontotherium is 

 distinct from Menodus and Megacerops; "Brontothe- 

 rium ingens," as used in later publications by Marsh, 

 referred to the skull, the type of "B. ingens," and not 

 to the jaw, the type of Brontotherium gigas. 



Brontotherium gigas Marsh, 1873 

 Cf. Brontotherium gigas, this monograph, page 567 



Original reference. — Am. Jour. Sci., 3d ser., vol. 5, 

 p. 486, 1873 (Marsh, 1873.1). 



Subsequent reference. — Principal characters of the 

 Brontotheriidae : Am. Jour. Sci., 3d ser., vol. 11, pi. 

 12, figs. 1-3, 1876 (Marsh, 1876.1). 



Type locality and geologic horizon. — Colorado; exact 

 locality and level not published. Sargent, Griswold, 

 and Marsh, collectors. 



Type. — "The present species is based on portions 

 of three individuals, one of which has the lower jaws 

 and entire molar series complete [lectotype]." Yale 

 Mus. 12009. (See fig. 165.) 



Characters of type. — The specific characters were 

 not separated by Marsh from the generic charcters. 

 Measurements of the lower jaw were given, some of 

 which (now verified) are as follows: 



Millimeters 



Length of lower jaw, from condyle to front of symphysis 634 



Depthof lower jaw, from top of coronoid process to angle 367 



Length of last lower molar 117 



Length of last lower premolar (Marsh gives this as 51) [49] 



Etymology. — yiyas, giant. 



Present determination. — This valid species is fully 

 discussed in Chapter VI of this monograph (p. 567). 

 Symborodon Cope, 1873 

 Cf. Menodus, this monograph, page 525 



Original reference. — Pal. Bull. No. 15, p. 2, "issued 

 August 20, 1873" (Cope, 1873.2). 



Subsequent reference. — Cope, Eeport on the verte- 

 brate paleontology of Colorado, pi. 2, fig. 1; pis. 3, 4, 

 1874 (Cope, 1874.2). 



Type species. — Symborodon tonus Cope. (See 

 below.) 



Generic characters. — Cope writes: 



Dentition: I.? 0; C. 1; Pm. 3; M. 3; the canines slightly 

 separated from each other, but not from the first premolar. 

 Crowns of the premolars with L-shaped crescents as in Rhi- 

 noceros; of the molars with completed crescents; the last molar 

 with third posterior crescent. Symphysis mandibuli coossi- 

 fied, crowns of canines not projecting, conic. * * * Xhe 

 genus differs from Titanotherium and Brontotherium in the 

 absence of incisors and from the former in the presence of but 

 three premolars. If there had been a deciduous incisor on each 

 side I was unable to detect any trace of it. 



Etymology. — (tvv, together; |Sop6s, devouring; oSous, 

 tooth; in reference to the approximation of the op- 

 posite canines toward the middle line. 



