Aktiogavialis
Encyclopedia
Aktiogavialis is an extinct genus
of crocodylian from the Oligocene Epoch some thirty million years ago. Only one species in the genus, Aktiogavialis puertoricensis, has been described so far.
As a typical gavialoid
, Aktiogavialis followed the standard crocodilia
n body plan. An elongated, squat quadruped
al body terminates in a long, laterally-flattened tail at one end and a specialized, narrow snout at the other. As with the other members of its family, the snout of Aktiogavialis was extremely long and narrow, tapering into a thin structure past the eye sockets
. Based on the fragmentary remains recovered, the species was differentiated from other members of its family by unique positioning and geometry of its skull elements. Phylogenetic analysis indicates that its closest relatives were the extinct gavials Gryposuchus
and Siquisiquesuchus
.
The type species of the genus, A. puertoricensis was described in 2007. The holotype
, designated UPRMP 3094, was discovered in Puerto Rican
deposits dating from the Oligocene
Epoch
some thirty million years old. The deposits, part of the San Sebastián
Formation along the Río Guatemala
in Puerto Rico, have been an adequate supply of other crocodylian fossils. Aktiogavialis remains recovered were extremely fragmentary, consisting of an incomplete skull
featuring elements of the braincase and other scattered cranial elements.
Marine sediments and nanofossils form part of the deposits where the specimen was found, indicating a marine distribution for Aktivogavialis puertoricensis. This is in contrast with the living gavialoids, which reside entirely in the freshwater rivers of South Asia
. While there is a possibility that fossils found in prehistoric delta
ic sediments have been washed onto the delta from inland sources, the Aktiogavialis specimen found so far was from a location that had essentially been island
ic. This has led to conclusions that gavialoids were partially or primarily saltwater reptiles prior to the evolution of the group's one or two extant species.
The genus' name, Aktiogavialis is derived from the Greek
words aktios (river) and gavialis (gavial). This roughly translates to "shore gavial", referring to Aktiogavialis rather estuarine distribution. The sole species' name, Aktiogavialis puertoricensis, mean "shore gavial from Puerto Rico", in reference to the specimen's country of origin.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of crocodylian from the Oligocene Epoch some thirty million years ago. Only one species in the genus, Aktiogavialis puertoricensis, has been described so far.
As a typical gavialoid
Gavialidae
Gavialidae is a family of reptiles within the order Crocodilia. Gavialidae consists of only one surviving species, the gharial , which is native to India. Many extinct species are also known...
, Aktiogavialis followed the standard crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
n body plan. An elongated, squat quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al body terminates in a long, laterally-flattened tail at one end and a specialized, narrow snout at the other. As with the other members of its family, the snout of Aktiogavialis was extremely long and narrow, tapering into a thin structure past the eye sockets
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
. Based on the fragmentary remains recovered, the species was differentiated from other members of its family by unique positioning and geometry of its skull elements. Phylogenetic analysis indicates that its closest relatives were the extinct gavials Gryposuchus
Gryposuchus
Gryposuchus is an extinct genus of gavialoid crocodilian. It is the type genus of the subfamily Gryposuchinae. Fossils have been found from Argentina, Colombia, Venezuela, Brazil and the Peruvian Amazon. The genus existed during the early and middle Miocene epoch. One recently described species, G...
and Siquisiquesuchus
Siquisiquesuchus
Siquisiquesuchus is an extinct genus of gavialoid crocodilian...
.
The type species of the genus, A. puertoricensis was described in 2007. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, designated UPRMP 3094, was discovered in Puerto Rican
Puerto Rico
Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...
deposits dating from the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
Epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...
some thirty million years old. The deposits, part of the San Sebastián
San Sebastián, Puerto Rico
San Sebastián is a municipality of Puerto Rico located northwest of the island south of Isabela and Quebradillas; north of Las Marías; east of Moca and Añasco; and west of Lares. San Sebastián is spread over twenty-four wards and San Sebastián Pueblo...
Formation along the Río Guatemala
Río Guatemala
-See also:*List of rivers of Puerto Rico-References:*USGS Hydrologic Unit Map – Caribbean Region *...
in Puerto Rico, have been an adequate supply of other crocodylian fossils. Aktiogavialis remains recovered were extremely fragmentary, consisting of an incomplete skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
featuring elements of the braincase and other scattered cranial elements.
Marine sediments and nanofossils form part of the deposits where the specimen was found, indicating a marine distribution for Aktivogavialis puertoricensis. This is in contrast with the living gavialoids, which reside entirely in the freshwater rivers of South Asia
South Asia
South Asia, also known as Southern Asia, is the southern region of the Asian continent, which comprises the sub-Himalayan countries and, for some authorities , also includes the adjoining countries to the west and the east...
. While there is a possibility that fossils found in prehistoric delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
ic sediments have been washed onto the delta from inland sources, the Aktiogavialis specimen found so far was from a location that had essentially been island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
ic. This has led to conclusions that gavialoids were partially or primarily saltwater reptiles prior to the evolution of the group's one or two extant species.
The genus' name, Aktiogavialis is derived from the 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;...
words aktios (river) and gavialis (gavial). This roughly translates to "shore gavial", referring to Aktiogavialis rather estuarine distribution. The sole species' name, Aktiogavialis puertoricensis, mean "shore gavial from Puerto Rico", in reference to the specimen's country of origin.