Cionodendron and related lithostrotionid genera from the Mississippian of eastern Australia: systematics, stratigraphy and evolution

• Published in: Alcheringa (Sydney) 2015-07, Vol.39 (3), p.315-376
• Main Authors: Denayer, Julien, Webb, Gregory E.
• Format: Article
• Language: English
• Subjects: Australastraea; Carboniferous; Cionodendron; convergence; corals; Earth sciences & physical geography; evolution; heterochrony; homeomorphy; Life sciences; Lithostrotionidae; palaeobiogeography; parallelism; phylogeny; Physical, chemical, mathematical & earth Sciences; Physique, chimie, mathématiques & sciences de la terre; Pickettodendron; rugose corals; Sciences de la terre & géographie physique; Sciences du vivant; Zoologie; Zoology
• ISSN: 0311-5518; 1752-0754
• DOI: 10.1080/03115518.2015.1001218

Denayer, J. & Webb, G.E., 26.2.2015. Cionodendron and related lithostrotionid genera from the Mississippian of eastern Australia: systematics, stratigraphy and evolution. Alcheringa 39, xxx-xxx. ISSN 0311-5518. The Mississippian colonial rugose corals of eastern Australia are taxonomically reviewed and assigned to formal genera. Their homeomorphy with the Eurasian genera Siphonodendron and Lithostrotion but also Heterostrotion resulted from parallel evolution within the Lithostrotionidae. Fasciculate species are reassigned to Cionodendron, as they share a robust columella, septotheca and two series of tabellae. Based on common characters, three species groups are recognized: the C. columen Group (characterized by the occurrence of parricidal and non-parricidal increase), the C. hallense Group (development of second-order lonsdaleoid dissepiments) and the C. arundineum Group (lacking the previous characters). Fourteen species are recognized, one being new (C. smithi sp. nov.) and two documented for the first time in the area. The oldest species are late Tournaisian in age, but the genus is most diverse in the middle-late Visean. Several morphological lineages are recognized within the three groups. The massive species are classified in the newly erected genus Australastraea that likely evolved from one of the early species of Cionodendron in the early Visean. Eleven species were identified, two being newly described (A. arcifera, sp. nov., A. carinata sp. nov.) and two others documented for the first time. Australastraea is characterized by a septotheca that is commonly discontinuous, conferring a pseudo-cerioid or astreoid habit. Two morphological groups are identified: the A. wilkinsoni Group (small corallites with simple narrow dissepimentarium) and the A. columnare Group (large corallites with complex dissepimentarium). The small fasciculate species previously referred to Lithostrotion williamsi are here reassigned to the new genus Pickettodendron, which differs from Cionodendron by the lack of minor septa and presence of a complete tabularium but is, nevertheless, relatively closely related to that genus. Pickettodendron is represented by three species, one being new (P. nudum sp. nov.), and is restricted to the early (-'middle') Tournaisian. A polyphyletic origin of the Cionodendroninae is considered, with Cionodendron and Australastraea originated in a first species of Amygdalophyllum and Pickettodendron originated in a second one. The biostratigraph