Kordikova. Turtles. Australia. Adelaide. 3

1. Kordikova, E.G. 1993. About the question of the homology of carapace elements in trionychids and other turtles. - Second Internat. Herpetolog. Congress, Adelaide, p. 141.
 https://doi.org/10.13140/RG.2.2.12631.07844

2. Kordikova, E.G. 1993. Fossil trionychids of Kazakhstan . - Second Internat. Herpetol. Congress, Adelaide, 1993, pp. 141-142.
https://doi.org/10.13140/RG.2.2.22697.40808

3. Kordikova, E.G. 1993. Peculiarities of postnatal  and individual  ontogenesis  of  trionychid skeletons. - Second Internat. Herpetol. Congress. Adelaide, 1993, pp. 142-143.
https://doi.org/10.13140/RG.2.2.20600.25605


1/
About the question of the homology of carapace elements in trionychids and other turtles.
ELENA G. KORDIKOVA. Institute of Zoology, 480032 Alma-Ata, Kazakhstan.

Thanks to the data on morphogenesis of skeletons received from the living trionychids and other turtles from different museums and institutes of Russia, Georgia and the USA, a new terminology of carapace elements based on principals of homology is discussed. So, it is known that neurals and costals of turtle carapaces are formed at the expense of corresponding neural arcs of vertebrae as well as ribs. This fact was reflected in the neural terminology of P. Meylan (1984) where the preneural is called by the first neural as the neural arc of the first vertebra and takes part in the formation of the first thoracic vertebra. Taking into account the morphogenesis of costals it is also necessary to change the numeration of costals as the rib of the first vertebra (which is usually reduced in most turtles) can take part in the formation of the real first costal (see specimen N PCHP 2771), the rib of the second one in the formation of the second costal, the rib of the third vertebra of the third one, etc. Thus, we follow Hasan (1941) and Meylan (1984) in considering the preneural of trionychids and other turtles whose phylogenetic relationships aren't disputed to be the first neural, the first neural to be the second one, etc. And we also suggest to change the terminology of costals: former first costal formed by the rib of the second vertebra is to be called by the second one, former second one by the third costal, etc. But, the rejection from traditional terminology of carapace elements in trionychids and other turtles will lead to some problems connected with the inconvenience of numeration of costals and neurals behind the second ones in most turtles. However, the suggested united terminology of carapace elements is the most adequate reflection of the formation and origin of the elements of the axial skeleton in turtles, their accordance to the organs in various organisms and it allows a critical appreciation of the traditional idea on the origin of trionychids and some other groups of turtles.
[KEYWORDS: homology, terminology, carapace, Trionychids].

2/
Fossil trionychids of Kazakhstan.
ELENA G. KORDIKOVA. Institute of Zoology, Kordikova 480032 Alma-Ata, Kazakhstan.

Fossil trionychids lived in Kazakhstan from the Late Cretaceous to the Middle Miocene and are referred to three groups, Ulutrionychini trib. nov., Paraplastomenini trib. nov. and Pelodiscini Meylan, 1987 represented by four genera (Ulutrionyx and Paraplastomenus gen. nov.) and ten species. Adult Ulutrionychines are characterised by the preservation of juvenile characters (relatively slight expansion of axial skeleton elements forming the carapace and plastron, the presence of postnuchal fontanelles, the absence of sculpture on peripheral parts of shell bones, etc.). Peculiar to the earlier stages of ontogenesis of most trionychids, and adult paraplastomenines (single genus Paraplastomenus) by the significant expansion of axial skeletal elements, including peripheral parts of the shell. The specific structure of the skull, the absence of the first neural, the presence of the reduced ninth pair of costals, etc., are characteristic for Ulutrionyx. The multiple adaptive radiation of the trionychids from an Asian continental center of origin of the distribution of the group is proposed. Ulutrionychine prochoreses probably took place in the Early Cretaceous of Middle Asia and Kazakhstan, in the Late Cretaceous Early Paleocene of North America through Beringia and in the Paleocene - Early Eocene - from North America to Europe. In the Early Eocene, Ulutrionychines invaded Central Kazakhstan, and from there appeared in the Early Miocene Asia Anterior, where now Rafetus euphraticus is present. Asian aspideretines probably were derived from the ancient Ulutrionychines. Paraplastomenine dispersal from the Asian continent probably happened in the Early Cretaceous of Middle Asia and Kazakhstan, then in the Late Paleocene Early Eocene of Kazakhstan and from there to West Europe through the Turgay bridge. Trionychines probably evolved from late paraplastomenines which came to Western Europe at the end of the Paleogene the beginning of the Neogene. Due to the connection between Europe and Africa, the Oligocene trionychids penetrated Africa where Trionyr triungulis lives now. The adaptive radiation of pelodiscines probably in the Asian continent. They inhabited Kazakhstan in the beginning of the Miocene and then expanded to South and East Asia where now Pelodiscus spp. live. But the Probability of a migration of Pelodiscines to North America must not be discarded. The similarity of Pelodiscus sinensis to Apalone mutica may confirm this supposition.
[KEYWORDS: fossil, Trionychids, Kazakhstan].

3/
Peculiarities of postnatal and individual ontogensis of trionychid skeletons.
ELENA G. KORDIKOVA. Institute of Zoology, 480032 Alma-Ata, Kazakhstan.

Numerous collections of living trionychid skeletons from different museums and institutes in Russia, Georgia and the US were investigated. It was established that the postnatal ontogenesis of the shell and axial skeleton occurs as follows: initially, the juvenile trionychids (particularly, Pelodiscus sinensis, Apalone spinifera, Platypeltis feror, Trionyx triunguis, etc.) haven't plates but ribs and defined thoracic vertebrae. They have an isolated unsculptured nuchal, that lies above the thoracic ribs and the separated rudiments of the hyo- and hypoplastrons. During the time of their growth, the nuchal, neural arcs of vertebrae, ribs and plastral elements are forming plates. And the nuchal begins to contact with the rib of the second thoracic vertebra and with the first (cyclanorbines and aspideretines) or with the second (most of the trionychids and other turtles) neural. The form of postnuchal fontanelles also changes with age: at first, the united transversal foramen is divided into two because of the contact of the medio-caudal part of the nuchal at the first or second neurals; sculpture appeared on callosities; costals and neurals as well as hyo- and hypoplastrons begin to contact with each other. During the turtles growth, neuro-costals and costal fontanelles at first, then postnuchal ones, begin to disappear along the whole carapace length. The anterior and posterior parts of the carapace have the most variability during the ontogeny of the skeleton. Variations of the skull and plastron bones happen rarely. Generally the remarked regularities characterised all members of this group. But, various trionychids of the same age have different degrees of skeleton development. So, callosities of the carapace and plastron elements appeared to be present in young specimens of Pelodiscus sinensis, in subadults of Trionys triunguis, in adults of Amyda cartilaginea. But, callosities scarcely developed in the oldest specimens of Dogania subplana. Analysis of individual characters can be different in comparison with the usual characters of familiar and subfamiliar range (the appearance of well-formed rib of the first thoracic vertebra and the corresponding costal, prenuchal, peripherals and the additional number of neurals and costals, where they are usually absent). The high degree of individual variability of Pelodiscus sinesis negates the separate status of the Far East trionychid. It was demonstrated, that the range of individual changes of the majority of skeleton elements is wide, so the complex use of characters for the identification of the fossil trionychids is appropriate in this case.
[KEYWORDS: variability, carapace, neurals, costals, Trionychids].