Herpetotherium

• H. fugax (syn. Didelphys pygmaea, H. scalare, H. tricuspis, Peratherium fugax) (type) • H. huntii • H. knighti (syn. Centracodon delicatus, Entomacodon minutus, Peratherium morrisi) • H. marsupium Troxell, 1923, p. 508 (syn. Peratherium marsupium according to Simpson, 1928) • H. merriami (Stock and Furlong, 1922, originally named within Peratherium as Stock agreed with Simpson that Herpetotherium Cope 1873 was synonymous with Peratherium) • H. tabrumi Korth, 2018 • H. valens (syn. Peratherium donahoei) • H. youngi (syn. Peratherium spindleri) ==Anatomy and morphology==

Herpetotherium has long been recognized as having a primitive morphology compared to other marsupials. For instance, Osborn (1907, p. 111) thought it represented an ancestral stock to both "later carnivorous and herbivorous types of marsupials", and thought it was evidence that polyprotodont opossum-like mammals must have given rise to other marsupials (Osborn, 1910, p. 154). Troxell (1923) strongly fixated on mandibular characters of Herpetotherium (though speaking specifically of H. marsupium, yet these are generally true of Herpetotherium) that he felt were especially comparable to Didelphis, such as "(1) the strong canine, (2) weak anterior premolar, (3) dominance of the protocone in the premolars, (4) fourth tooth of the series molariform, (5) position of mental foramen under this tooth, (6) identical form of the molars, (7) groove on the jaw suggesting an inflected angle," yet he pointed out several differences, such as "(1) absence of diastemata around the anterior premolar, (2) trend of the mental foramen forward instead of backward, (3) the inflected angle, seeming to begin beneath the molars" (p. 510). ==References==