Regulus bulgaricus
Encyclopedia
Regulus bulgaricus is a fossil passerine
from the Middle Villafranchian (lower Pleistocene
to upper Pliocene
) of Bulgaria
. This bird is a member of the kinglet
family and genus, and is the only fossil kinglet found so far. It is known from a single ulna
, which is 13.3 mm long. The fossil was discovered in 1991 near Varshets, Bulgaria, and described by Zlatozar Boev.
near Varshets, Bulgaria. It was first described by its collector, the Bulgarian paleornithologist Zlatozar Boev. Its species name, bulgaricus, was given after the country in which the fossil was found. Boev diagnosed it as an extinct species of the genus Regulus. The ulna is smaller than that of most passerines, and the shape of the articular surfaces identify it as a kinglet. It is distinguished from R. regulus by a thicker base, a longer olecranon
, a larger cotyla dorsalis
, and smaller quill knobs (papillae remigales caudales). Compared to R. ignicapilla, R. bulgaricus has a narrower proximal part of the diaphysis
, a shorter olecranon, and smaller tuberculum retinaculi. Although Boev was unable to compare the fossil ulna with R. Goodfellowi, it can be excluded from this taxonomical comparison due to it sharing a superspecies with R. regulus.
Regulus bulgaricus is the only fossil kinglet, and is possibly the ancestor of R. ignicapillus. This was speculated based on the postglacial origin of a coniferous forest belt in the Holarctic
, which means that its avifauna is of a more recent origin.
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
from the Middle Villafranchian (lower Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
to upper Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
) of Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
. This bird is a member of the kinglet
Kinglet
The kinglets or crests are a small group of birds sometimes included in the Old World warblers, but are frequently given family status because they also resemble the titmice. The scientific name Regulidae is derived from the Latin word regulus for "petty king" or prince, and comes from the...
family and genus, and is the only fossil kinglet found so far. It is known from a single ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
, which is 13.3 mm long. The fossil was discovered in 1991 near Varshets, Bulgaria, and described by Zlatozar Boev.
Taxonomy
The only known specimen of Regulus bulgaricus is a complete left ulna, 13.3 mm in length. It was collected on 20 September 1991 in a ponorPonor
A ponor is a natural surface opening that may be found in landscapes where the geology and the geomorphology is characterized by some kind of karst....
near Varshets, Bulgaria. It was first described by its collector, the Bulgarian paleornithologist Zlatozar Boev. Its species name, bulgaricus, was given after the country in which the fossil was found. Boev diagnosed it as an extinct species of the genus Regulus. The ulna is smaller than that of most passerines, and the shape of the articular surfaces identify it as a kinglet. It is distinguished from R. regulus by a thicker base, a longer olecranon
Olecranon
The olecranon is a large, thick, curved bony eminence of the forearm that projects behind the elbow.It is situated at the upper end of the ulna, one of the two bones in the forearm...
, a larger cotyla dorsalis
Upper extremity of ulna
The upper extremity of the ulna presents two curved processes, the olecranon and the coronoid process; and two concave, articular cavities, the semilunar and radial notches.- The olecranon :...
, and smaller quill knobs (papillae remigales caudales). Compared to R. ignicapilla, R. bulgaricus has a narrower proximal part 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 shorter olecranon, and smaller tuberculum retinaculi. Although Boev was unable to compare the fossil ulna with R. Goodfellowi, it can be excluded from this taxonomical comparison due to it sharing a superspecies with R. regulus.
Regulus bulgaricus is the only fossil kinglet, and is possibly the ancestor of R. ignicapillus. This was speculated based on the postglacial origin of a coniferous forest belt in the Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...
, which means that its avifauna is of a more recent origin.