One of the best articles I have read on this subject came from the materials of authors Z.Qiu & N.Kittler (1983). For those of you interested, I can try to recap some of the key points and answer any questions:
THE DISTINCTION BETWEEN AGRIOTHERlUM AND INDARCTOS
Indarctos was first separated from Hyaenarctos by Pilgrim in 1913 chiefly by its enlarged talon of M2/. Owing to the absence of veritable association of upper and lower dentitions, in the ensuing 20 years the discussion had been mainly restricted to the characters of the upper dentition. Zdansky's adoption of the differentiation of the two genera was based exactly on the characters of M2/, as proposed by Pilgrim in 1913. Frick, while considering Indarctos one of this three subgenera of the genus Hyaenarctos, dwelt on P4/-M 1 in 1926. Matthew's correct summary of the differences of the two genera in 1929 was based also on P4 -M1. Pilgrim was the first to combine the lower dentition, namely M/1 with the upper ones in his diagnostic characters for the two genera and his viewpoints have been subsequently widely accepted. According to this author, the most important characters, by which Agriotherium differs from Indarctos, with exception of the less important position of the zygomatic arch, are:
1. P1 to P3 are small, single-rooted teeth; one lower premolar is missing. 2. Inner border of the upper molars shorter than the outer border. 3. M2/ without talon. 4. P4/ with antero-posterior diameter greater than that of M1/; parastyle prominent. 5. M/1 relatively short, with talonid much shorter than trigonid, and hypoconid higher than entoconid.