Santanachelys
Encyclopedia
Santanachelys gaffneyi is the earliest known sea turtle
. It is the only species in the genus Santanachelys, which itself is a member of the extinct family
Protostegidae
. The species was first described from a 20-centimeter long fossil
specimen unearthed in 1998 in Eastern Brazil
. Due to the rock layer from which it was excavated, it was determined that the specimen was from the Early Cretaceous
period some 110 million years old.
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 paddles that modern sea turtles possess, the early sea turtle's digits were distinct and movable similar to that of non-marine
turtles. Like later sea turtles though, Santanachelys had large salt gland
s situated near its eyes which allowed it to drink saltwater without dehydration
.
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 the turtle's skull where salt gland
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 the line's paddles.
Taxonomically
, Santanachelys has been placed in the family
Protostegidae
along with many other extinct sea turtles. It is the earliest member of the family to date, and the earliest known member of the sea turtle superfamily
, Chelonioidea. Cladistically
, it is the sister taxon
to the rest of the later protostegids, including Protostega
and Notochelone
. As a member of its family, its closest living relative belongs to the family Dermochelyidae
, the leatherback turtle.
Its genus, Santanachelys was named for the Santana Formation
, the locality where the fossil was found and chelys, Greek
for "turtle". The species name, S. gaffneyi was named in honor of Eugene S. Gaffney
, a paleontologist who specialized in turtle
phylogeny.
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...
. It is the only species in the genus Santanachelys, which itself is a member of the extinct family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Protostegidae
Protostegidae
Protostegidae is a family of extinct marine turtles that lived during the Mesozoic Era. The family includes some of the largest sea turtles that ever existed. The largest, Archelon, had a head a meter long...
. The species was first described from a 20-centimeter long fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
specimen unearthed in 1998 in Eastern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. Due to the rock layer from which it was excavated, it was determined that the specimen was from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
period some 110 million years old.
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 paddles that modern sea turtles possess, the early sea turtle's digits were distinct and movable similar to that of non-marine
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
turtles. Like later sea turtles though, Santanachelys had large salt gland
Salt gland
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...
s situated near its eyes which allowed it to drink saltwater without dehydration
Dehydration
In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
.
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 the turtle's skull where salt gland
Salt gland
The salt gland is an organ for excreting excess salts. It is found in elasmobranchs, seabirds, and some reptiles. In sharks, salt glands are found in the rectum, but in birds and reptiles, they are found in or on the skull, in the area of the eyes, nostrils or mouth. In crocodiles, the salt is...
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 the line's paddles.
Taxonomically
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
, Santanachelys has been placed in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Protostegidae
Protostegidae
Protostegidae is a family of extinct marine turtles that lived during the Mesozoic Era. The family includes some of the largest sea turtles that ever existed. The largest, Archelon, had a head a meter long...
along with many other extinct sea turtles. It is the earliest member of the family to date, and the earliest known member of the sea turtle superfamily
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...
, Chelonioidea. Cladistically
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
, it is the sister taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
to the rest of the later protostegids, including Protostega
Protostega
Protostega gigas is an extinct species of marine turtle. It was first collected from the Smoky Hill Chalk of western Kansas in 1871, and named by E.D. Cope...
and Notochelone
Notochelone
Notochelone is an extinct genus of sea turtle, which existed about 100 million years ago. The species was first described by Richard Lydekker in 1889. It was the most common marine reptile living in the inlands of the sea around Queensland, Australia. It was a small turtle, and was about the same...
. As a member of its family, its closest living relative belongs to the family Dermochelyidae
Dermochelyidae
Dermochelyidae is a family of turtles which has eight extinct and one extant genera.-Classification of known genera:*Subfamily Desmatochelyinae** Corochelys ** Desmatochelys *Subfamily Allopleuroninae ** Allopleuron ** Eosphargis...
, the leatherback turtle.
Its genus, Santanachelys was named for the Santana Formation
Santana Formation
The Santana Formation is a geologic Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau...
, the locality where the fossil was found and chelys, Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
for "turtle". The species name, S. gaffneyi was named in honor of Eugene S. Gaffney
Eugene S. Gaffney
Eugene S. Gaffney is an American paleontologist and leading authority on the evolutionary history of turtles.-Biography:He graduated from Rutgers State University in 1965; and received his PhD in 1969 with a thesis on "The North American Baenoidea and the Cryptodire-Pleurodire Dichotomy" from...
, a paleontologist who specialized in turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
phylogeny.