This area yielded numerous fossil vertebrates including several ornithurine birds (CLARKE & CHIAPPE, 2001; AGNOLIN, 2010a; AGNOLIN & NOVAS, 2011), abelisaurid, titanosaurid, and dromaeosaurid
dinosaurs (CORIA, 2001; MARTINELLI & FORASIEPI, 2004, NOVAS et al.
We interpret the sickle claw of dromaeosaurids as having evolved to do the same thing: latching in, and holding on," he said.
Other features of bird of prey feet gave clues as to the functional anatomy of their ancient relatives, toe proportions of dromaeosaurids seemed more suited for grasping than running, and the metatarsus, the bones between the ankles and the toes, is more adapted for strength than speed.
A long metatarsus lets you take bigger strides to run faster; but in dromaeosaurids, the metatarsus is very short, which is odd," he said.
The study also has implications for the next closest relatives of troodontids and dromaeosaurids, the birds.
We see fully formed wings in exquisitely preserved dromaeosaurid fossils, and from biomechanical studies we can show that they were also able to perform a rudimentary flapping stroke.
Previously unearthed fossils suggested that dromaeosaurids lived in the Southern Hemisphere, but the new find seals the case, says Makovicky.
The new find indicates that dromaeosaurids were far more widespread than previously recognized, says Mark A.
Dromaeosaurids had the same joint arrangement as did early birds such as Archaeopteryx, Holtz adds.
Overall, researchers have found four specimens, all far south of where any indisputable dromaeosaurid remains have ever been discovered.
The currently known Portuguese record of dromaeosaurids is very scarce and these theropods are only represented by some teeth described from the Guimarota coalmine, and by scarce elements collected in the Upper Cretaceous from the northern area of the Lusitanian Basin (Galton, 1996; Zinke, 1998).
Based on these characters, it is considered the presence in Andres of a representative of the dromaeosaurids that shares some conditions with Dromaeosaurus.
As one of the earliest and most complete dromaeosaurids
, Sinornithosaurus helps fill in critical information, says Wu.