Santanachelys Gaffneyi
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''Santanachelys gaffneyi'' is an extinct species of
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerh ...
. It is the only species in the genus ''Santanachelys'', which itself is a member of the
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Protostegidae Protostegidae is a family of extinct sea turtle, marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest ''Archelon'' had a head long. Like most sea turtles, the ...
. The species was first described from a 20-centimeter long
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
specimen unearthed in 1998 from the
Santana Formation The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian s ...
of eastern
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
. From the rock layer from which it was excavated, it was determined that the specimen was from the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
period (112 million years old). It is therefore one of the oldest known sea turtles. but a new fossil named ''
Desmatochelys ''Desmatochelys'' (from Greek δεσμός ''desmos'' 'link' + χέλῡς ''khelus'' ‘tortoise’) is an extinct genus of sea turtles belonging to the family Protostegidae. This genus contains two known species, ''D. lowii'' and ''D. padillai' ...
'' ''padillai'' in 2015 is estimated to be as old as 120 million years. While the specimen showed many characteristics of modern sea turtles, it differed from the typical sea turtle body plan in several ways. One glaring difference is that ''Santanachelys'' had distinguishable digits at the tip of its forearms. Instead of the fully fused,
hydrodynamic In physics, physical chemistry and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids – liquids and gases. It has several subdisciplines, including (the study of air and other gases in moti ...
paddles that modern sea turtles possess, the early sea turtle's digits were distinct and movable similar to those of non- marine turtles. Like later sea turtles though, ''Santanachelys'' had large
salt gland The salt gland is an organ (anatomy), organ for excreting excess salt (chemistry), salts. It is found in the cartilaginous fishes subclass elasmobranchii (sharks, rays, and skates), seabirds, and some reptiles. Salt glands can be found in the r ...
s situated near its eyes, which aided in the excretion of excess salt. This was an adaptation to the highly saline marine environment. Evolutionarily, the morphology of ''Santanachelys'' is typical of what is expected of an early sea turtle. The front appendages not being fully evolved into flippers is a sign of this. The presence of large
foramen In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, artery, ...
in the turtle's skull where
salt gland The salt gland is an organ (anatomy), organ for excreting excess salt (chemistry), salts. It is found in the cartilaginous fishes subclass elasmobranchii (sharks, rays, and skates), seabirds, and some reptiles. Salt glands can be found in the r ...
s were is an interesting evolutionary point. It is pointed out that this suggests that the evolutionary return to oceanic waters of the sea turtle line evolved before the finalization and streamlining of its paddles.
Taxonomically In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...
, ''Santanachelys'' has been placed in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Protostegidae Protostegidae is a family of extinct sea turtle, marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest ''Archelon'' had a head long. Like most sea turtles, the ...
along with many other
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
sea turtles. It is the earliest member of the family to date, and the earliest known member of the sea turtle
superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...
,
Chelonioidea Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...
.
Cladistically Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
, it is the sister
taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
to the rest of the later protostegids, including ''
Protostega ''Protostega'' ('first roof') is an extinct genus of sea turtle containing a single species, ''Protostega gigas''. Its fossil remains have been found in the Smoky Hill Chalk formation of western Kansas (''Hesperornis'' zone, dated to 83.5 millio ...
'' and '' Notochelone''. As a member of its family, its closest living relative belongs to the family
Dermochelyidae Dermochelyidae is a family of sea turtles which has seven extinct genera and one extant genus, containing one living species, the leatherback sea turtle (''Dermochelys coriacea''). The oldest fossils of the group date to the Late Cretaceous ...
, the leatherback turtle. Its genus, ''Santanachelys'' was named for the
Santana Formation The Santana Group is a geologic group, formerly included as the middle part of the Araripe Group, in the Araripe Basin of northeastern Brazil. The group comprises the Crato, Ipubi and Romualdo Formations and is dated to the Aptian to Albian s ...
, the locality where the fossil was found and ''chelys'',
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
for "turtle". The species name, ''S. gaffneyi'' was named in honor of Eugene S. Gaffney, a
paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
who specialized in
turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...
phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...
.


Fossils

As of 2023, two fossils of the species had been identified. The
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
specimen was described in 1998, and was deposited in the
Teikyo Heisei University is a private university Private universities and private colleges are higher education institutions not operated, owned, or institutionally funded by governments. However, they often receive tax breaks, public student loans, and government gran ...
fossil collections in Japan. Beginning in 2012, the Brazilian government has unsuccessfully attempted to repatriate the fossil, but as of 2023 it remains at
Waseda University Waseda University (Japanese: ), abbreviated as or , is a private university, private research university in Shinjuku, Tokyo. Founded in 1882 as the Tōkyō Professional School by Ōkuma Shigenobu, the fifth Prime Minister of Japan, prime ministe ...
. After being part of the
University of Zurich The University of Zurich (UZH, ) is a public university, public research university in Zurich, Switzerland. It is the largest university in Switzerland, with its 28,000 enrolled students. It was founded in 1833 from the existing colleges of the ...
Department of Palaeontology for over 30 years and labeled simply as "Testudines indet.", the second fossil was described in 2023. The fossil had been altered and illegally sold by fossil dealers, in contravention of
Brazilian law The law of Brazil is based on statutes and, partly and more recently, a mechanism called ''súmulas vinculantes''. It derives mainly from the European civil law systems, particularly the Portuguese, the Napoleonic French and the German (espec ...
. Using
CT scans A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...
, it was revealed that the bottom half of the specimen was a
chimera Chimera, Chimaera, or Chimaira (Greek for " she-goat") originally referred to: * Chimera (mythology), a fire-breathing monster of ancient Lycia said to combine parts from multiple animals * Mount Chimaera, a fire-spewing region of Lycia or Cilicia ...
created from parts of a ''
Araripemys ''Araripemys'' is an extinct marine turtle genus from 112 to 109 million years ago, in the Early Cretaceous Crato and Romualdo Formations of the Araripe Basin in northeastern Brazil Brazil, officially the Federative Republic of Brazil, ...
'' turtle fossil in combination with indeterminate fragments of shell. In 2023, the fossil was described and repatriated, being deposited at
Federal Rural University of Pernambuco The Federal Rural University of Pernambuco (, UFRPE) is a public university in Recife, Pernambuco, Brazil. Specializing in courses in agricultural sciences and other courses relating to rural development, the university also conducts research in t ...
, in Brazil.


References

{{Testudines Protostegidae Prehistoric turtle genera Monotypic prehistoric reptile genera Early Cretaceous turtles Early Cretaceous reptiles of South America Cretaceous Brazil Fossils of Brazil Fossil taxa described in 1998 Extinct turtles