Description. Type species Ammonites numidus Coquand, 1880. According to Kennedy and Klinger (1979), this is a moderately evolute genus with a rounded or rectangular whorl section. The shell is smooth or ornamented with fine, more or less radial lirae. Constrictions are present in some species and can become pronounced. As in other Gaudryceratidae, the internal (dorsal) suture is reduced to the dorsal saddle, with much smaller additional saddles in some species. This genus is found in the Lower Cretaceous, from the Barremian to the Upper Albian, in France, Spain, England, Bulgaria, Italy, Switzerland, the Caucasus, Algeria, Egypt, South Africa, Madagascar, California, and Antarctica.
Sous-genres. The genus Eogaudryceras includes two subgenera, Eogaudryceras sensus stricto and Eotetragonites.
The subgenus Eogaudryceras, type E. numidum (Coquand), has a whorl cross-section that is initially trapezoidal, then becoming rounded and sometimes compressed in the adult. The test shows fine, sinuous lirae projecting forward on venter, but the internal mold is smooth. Constrictions are absent or weakly developed, typically limited to the inner whorls. The suture includes symmetrically bifid saddles and a large suspensive lobe. The age and geographic distribution are those of the genus. The top photograph shows E. (Eogaudryceras) numidum (Coquand, 1879).
The subgenus Eogaudryceras (Eotetragonites) Breistroffer, 1947 (type E. raspaili Breistroffer), is thought to have derived from the former during the Late Aptian. It has a rather depressed whorl section at first, more angular or rectangular than in E. (Eogaudryceras) at all growth stages. The smooth or finely striated shell shows moderate to strong constrictions at all ages, crossing venter with a moderate proverse sinus. The saddles of the suture line are asymmetrically bifid, and the internal (dorsal) suture shows a main saddle, a first lateral saddle, and a rudimentary second lateral saddle. Eotetragonites is found from Lower Aptian to Middle Albian in the regions already mentioned for the genus, except in Algeria and England. The lower photograph illustrates an E. (Eotetragonites) umbilicostriatusCollignon, 1963.
Remarks. Some authors, such as Hoffmann (2010), consider the division of the genus Eogaudryceras into two subgenera to be unfounded. Others, such as Spath (1927), restrict it to forms without constrictions.