Branta thessaliensis
Encyclopedia
Branta thessaliensis is a prehistoric species
of black goose
known from fossils found in Greece
. It is among the earliest known members of its genus
.
Described in 2006, it was of similar size to the Canada Goose
. It is known from a humerus
bone, which differs form the living species by a wider distal end of the diaphysis
, a dorsal condyle that is more rounded in dorsal
view and more prominent compared to the ventral condyle in distal view, and a deeper humerotricipital sulcus in distal view.
The fossil was found in a Late Miocene
(Middle Turolian
: European Mammal Neogene stage MN12, 7.5-6.8 million years ago) deposit at Perivolaki in Thessaly
, after which region the species was named. Both near-shore freshwater
bodies and open grassland
habitat
were found in the Perivolaki area during MN12.
The species provides further support for the distinctness of Branta from the Anser
grey geese by that time. It also suggests that the present biogeography
of Eurasian Branta - breeding at Arctic
and wintering at Mediterranean latitude
s - is a product of post-Miocene times, possibly due to range shifts during the ice age
era. In this aspect it is notable that such a breeding-wintering range disjunction is less pronounced in the Canada and Cackling Geese
of North America, where unlike in there was no W-E barrier (the Alpide belt
) barring range shifts in response to the advancing ice.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of black goose
Branta
The black geese of the genus Branta are waterfowl belonging to the true geese and swans subfamily Anserinae. They occur in the northern coastal regions of the Palearctic and all over North America, migrating to more southernly coasts in winter, and as resident birds in the Hawaiian Islands...
known from fossils found in Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
. It is among the earliest known members of its genus
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...
.
Described in 2006, it was of similar size to the Canada Goose
Canada Goose
The Canada Goose is a wild goose belonging to the genus Branta, which is native to arctic and temperate regions of North America, having a black head and neck, white patches on the face, and a brownish-gray body....
. It is known from a humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
bone, which differs form the living species by a wider distal end of the diaphysis
Diaphysis
The diaphysis is the main or mid section of a long bone. It is made up of cortical bone and usually contains bone marrow and adipose tissue ....
, a dorsal condyle that is more rounded in dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
view and more prominent compared to the ventral condyle in distal view, and a deeper humerotricipital sulcus in distal view.
The fossil was found in a Late Miocene
Late Miocene
The Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....
(Middle Turolian
Turolian
The Turolian age is a period of geologic time within the Miocene used more specifically with European Land Mammal Ages. It precedes the Ruscinian age and follows the Vallesian age. The Turolian overlaps the Tortonian and Messinian ages....
: European Mammal Neogene stage MN12, 7.5-6.8 million years ago) deposit at Perivolaki in Thessaly
Thessaly
Thessaly is a traditional geographical region and an administrative region of Greece, comprising most of the ancient region of the same name. Before the Greek Dark Ages, Thessaly was known as Aeolia, and appears thus in Homer's Odyssey....
, after which region the species was named. Both near-shore freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
bodies and open grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
were found in the Perivolaki area during MN12.
The species provides further support for the distinctness of Branta from the Anser
Anser (genus)
The waterfowl genus Anser includes all grey geese and sometimes the white geese. It belongs to the true geese and swan subfamily . The genus has a Holarctic distribution, with at least one species breeding in any open, wet habitats in the subarctic and cool temperate regions of the Northern...
grey geese by that time. It also suggests that the present biogeography
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
of Eurasian Branta - breeding at Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
and wintering at Mediterranean latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
s - is a product of post-Miocene times, possibly due to range shifts during the ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
era. In this aspect it is notable that such a breeding-wintering range disjunction is less pronounced in the Canada and Cackling Geese
Cackling Goose
The Cackling Goose is a North American bird of the genus Branta of black geese, which contains species with largely black plumage, distinguishing them from the grey Anser species....
of North America, where unlike in there was no W-E barrier (the Alpide belt
Alpide belt
The Alpide belt is a mountain range which extends along the southern margin of Eurasia. Stretching from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic, it includes the Alps, the Carpathians, the mountains of Asia Minor and Iran, the Hindu Kush, the Himalayas,...
) barring range shifts in response to the advancing ice.