|mhorn||Дата: Tuesday, 18.09.2012, 09:13 | Сообщение # 1|
|Cantú Chapa A. (2012) The suture line patterns in Olcostephanidae and Spiticeratidae, ammonites of the Upper Jurassic – Lower Cretaceous: systematic considerations // Paleontología Mexicana, Vol.62, P.52-66 |
This paper provides review of olcostephanid systematics based primarily on the structure of S1 and S2 saddles as well as other features of septal suture and sculptural differences. Two other approaches, focused on proposed dimorphism within genera (i.e. Wright et al., 1996) or changes of septal suture through ontogeny (i.e. Kvantaliani et al., 1999) are only briefly reviewed. The author called concept of sexual dimorphism in ammonites as “mythical”. Two families are recognized - Spiticeratidae Spath, 1924 (with bifurcate S1) and Olcostephanidae Haug, 1910 (with trifurcate S1); structure of S2 saddle as well as relative size and form of saddles and lobes are considered among the important features. Many new taxa are proposed: Groebericeratinae n. subfam., Saynoceratinae n. subfam., Garcitinae n. subfam., Kurdistanites n. gen., Peruvites n. gen., Spiticeras (Djanelidzeites) n. subgen. Suborder Olcostephanina by Kvantalian et al. is rejected because septal suture figured for this suborder (Kvantaliani et al., fig. 22) differ significantly from those of olcostephanids (this is septal suture of boreal dorsoplanitid Laugeites). In my opinion, this “Suborder” is polyphyletic and includes superfamilies and families of perisphinctoid, which showing some common features due toi homeomorphy but which are not directly connected phylogenetically. Unfortunately focusing on mainly mature septal suture with little attention to other data lead to some errors. Thus, fig. 8 demonstrates the following succession as “phylogenetical”: Idoceras (Lower Kimmeridgian), Aulacostephanus Upper Kimmeridgian) and Proniceras (Upper Tithonian). Septal sutures of these genera are relatively close to each other, but they are belongs to different families which are not connected. Further usage of S1 and S2 saddles for ammonite systematics could be interesting but need checking with more material.
Middle Jurassic - Lower Cretaceous ammonites & aptychi