The Miocene tortoiseTestudo catalaunicaBataller, 1926, and a revised phylogeny of extinct species of genusTestudo(Testudines: Testudinidae)

Quaternary megafauna extinctions altered body size distribution in tortoises

The late Quaternary is characterized by the extinction of many terrestrial megafauna, which included tortoises (Family: Testudinidae). However, limited information is available on how extinction shaped the phenotype of surviving taxa. Here, based on a global dataset of straight carapace length, we investigate the temporal variation, spatial distribution and evolution of tortoise body size over the past 23 million years, thereby capturing the effects of Quaternary extinctions in this clade. We found a significant change in body size distribution characterized by a reduction of both mean body size and maximum body size of extant tortoises relative to fossil taxa. This reduction of body size occurred earlier in mainland (Early Pleistocene 2.588-0.781 Ma) than in island tortoises (Late Pleistocene/Holocene 0.126-0 Ma). Despite contrasting body size patterns between fossil and extant taxa on a spatial scale, tortoise body size showed limited variation over time until this decline. Body size is a fundamental functional trait determining many aspects of species ecologies, with large tortoises playing key roles as ecosystem engineers. As such, the transition from larger sized to smaller sized classes indicated by our findings likely resulted in the homogenization of tortoises' ecological functions and diminished the role of tortoises in structuring the vegetation community.

The latest Miocene to Pliocene small-sized fossil turtles, Testudinidae and Geoemydidae, from Makrygialos, Thermaikos Gulf, Northern Greece

Although the existence of fossil turtles in Makrygialos and the surrounding areas, on the west side of the Thermaikos Gulf in Northern Greece, has been known for almost two decades, it has not been studied so far in detail. Over the last 5 years, we have conducted systematic fieldwork and exploration, focusing on the discovery and recovery of fossils in the coastal broader area of Makrygialos. Eleven turtle specimens have been found so far, eight of which have been collected, on the outcrops of the beaches of Makrygialos and Agiannis. Their age is estimated between the latest Miocene and Pliocene. Four of these specimens are terrestrial giant tortoises, two of them are small tortoises which we identify as the species Chersine hermanni sensu lato, and the last two are freshwater turtles which we attribute to the genus Mauremys sensu lato. Here, we present our studies on the small-sized turtle species from this region. The fossil turtle fauna of Makrygialos is among the richest and most diverse in Greece, as in only a few other Greek localities at least three species of fossil turtles have been found. The C. hermanni specimens found in Makrygialos are probably the oldest fossils of the species found in Europe. The small-turtle faunal composition during the Neogene along the east and west sides of the Thermaikos Gulf was completely different.

Total evidence analysis and body size evolution of extant and extinct tortoises (Testudines: Cryptodira: Pan-Testudinidae)

Testudinidae (tortoises) is an extant clade of terrestrial turtles of worldwide distribution and with a rich fossil record that provides an exceptional context for studying their evolutionary history. Because of the lack of global phylogenetic analyses integrating extinct taxa, our current knowledge of the relationships of the total clade of Testudinidae is rather poor. To resolve this issue, we performed the first total evidence analysis of Pan-Testudinidae. The total evidence trees are congruent with the molecular topology and agree on the dichotomy of derived Testudinidae (=Testudininae; Converted Clade Name) into two previously recognized major clades, Testudona and Geochelona (New Clade Name). The integration of extinct taxa into the analysis allowed the stratigraphic fit of the total evidence trees, indicating that crown Testudininae, Testudona and Geochelona all originated by the Late Eocene, in agreement with recent molecular estimates. Ghost lineage analysis indicates high diversification in the Late Eocene and in the Miocene. The age of crown Testudo is Late Miocene, again in accordance with some molecular dates. Phylogenetic placement of fossils demonstrates that giant body size independently evolved in multiple continental mainland taxa and confirms recent results deduced from living taxa-giantism in Testudinidae is not linked to the insular effect. An unexpected outcome is the recovery of miniaturization in Testudona (<30 cm carapace length) that emerged sometime between the Oligocene and Early Miocene. No clear correlation between body size evolution and climate is apparent, but increased taxon sampling may nevertheless demonstrate the role of cooling and warming as one of many influential variables.