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Related to Urostyle: keel bone


(vertebrate zoology)
An unsegmented bone representing several fused vertebrae and forming the posterior part of the vertebral column in Anura.



a rodlike bone in the caudal portion of the vertebral column of some vertebrates, formed by the fusion of all caudal vertebrae (in salientians) or of only the terminal caudal vertebrae (in bony fishes). Together with the hypural bones, the urostyle supports the radials of the homocercal fin of bony fishes.

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satan differs from this genus in having a more developed squamosal lamina, wider and shallower orbital margin of the maxilla, dorsoventrally taller and transverselly compressed proximal end of urostyle, and medially tilted dorsal margin of ilium (CASAMIQUELA, 1958, 1961; Appendix 3; see below).
The genus Gigantobatrachus was recovered in the present analysis as the sister group of Calyptocephalella, both conforming a clade sustained by three synapomorphies: 1-presence of very well-developed dorsal iliac crest, 2- urostyle as long as presacral column, and 3- short and curved clavicle (see Appendix 3).
Moreover, these specimens belong to the genus Gigantobatrachus because of its gigantic size (the largest known taxon within the family), external ornamentation composed by very deep and wide pits separated by strong osseous ridges (see CASAMIQUELA, 1958), proximal articular end of urostyle strongly dorsoventrally compressed and transversally expanded (unambiguous synapomorphy of Gigantobatrachus; Appendix 3), and very small and deeply concave orbital margins of the maxilla (unambiguous synapomorphy of Gigantobatrachus; Appendix 3).
Sacral vertebra and urostyle: 0--articulated; 1--fused.
Urostyle length compared to total presacral length: 0--lower; 1--subequal (REIG, 1960a,b).
ULABG 463 with anterior part of dorsum greenish-brown, and irregular dark spots on top of head, at level of shoulders and sacral and urostyle regions; inguinal band broken in dots towards anterior part (on right flank); belly whitish, throat uncolored, darker than belly; pale tympanum.
Counts were made from a radiograph of the holotype and from each specimen where possible; vertebral counts include the urostyle. The first caudal vertebra is that with the haemal spine supporting the first anal-fin ray.
Myomeres were difficult to count reliably at either end and thus vertebral counts (which include the urostyle) of stained larvae were taken instead.
Measurements were taken from the tip of the snout to the end of the notochord in preflexion larvae (notochord length), and from the tip of the snout to the end of the urostyle or hypural plate (whichever was more distal) in flexion or postflexion larvae (standard length).