Discovery and naming
In 1975, fossil-bearing deposits of the Lecho Formation were discovered at the locality of El Brete, Salta Province, Argentina by a team from the Fundación Miguel Lillo. [2] In the years after this, Argentine paleontologist José Bonaparte carried out field surveys at this site. Among the discoveries made were about 60 fossilised bird bones, which were added to the collection of the National University of Tucumán. In 1981, British paleontologist Cyril Walker published a study in which he illustrated some of these bones and determined that while they represent multiple species, all of them would have been members of a group which he named the Enantiornithes. In particular, he points out that three types of tarsometatarsi (one of the bones in a bird leg) are present in the collection. [3]
Twelve years after Walker's study was published, Argentine paleontologist Luis M. Chiappe studied the bird tarsometatarsi from El Brete and named each of the three types as new genera and species, one of which was given the name Soroavisaurus australis. The generic name combines the Latin word soror (meaning "sister") with Avisaurus (another fossil bird), as Chiappe determined these two types of birds to be close relatives, while the specific name means "southern". He designated a left tarsometatarsus with the specimen number PVL-4690 as the holotype of this species, in addition to referring another specimen (PVL-4048) to it. [4] Both of these specimens were formerly thought to be remains of a species of Avisaurus. [5] [6]
More of the enantiornithine specimens from El Brete have been referred to Soroavisaurus after the genus was erected, though some of these referrals have been questioned. In 2002, Walker and Chiappe worked together on a study which considered the specimens PVL-4030 and PVL-4033 to be fossilised tibiotarsi (another bone in a bird leg) of Soroavisaurus. [7] Walker had previously considered both of these specimens to be comparable to Martinavis , referring to both as cf. Martinavis in an unpublished manuscript. In 2009, he authored another study with Irish paleontologist Gareth J. Dyke which once again finds PVL-4030 to be a Martinavis specimen, assigning it to an unnamed species of the genus. However, this study still considers PVL-4033 to be a Soroavisaurus tibiotarsus. [8]
Description
The specimens are in the collection of the Fundación-Instituto Miguel Lillo, Tucumán. They are cataloged as PVL-4690, a 46.9 mm (1.85 in)-long left tarsometatarsus, and PVL-4048, which includes another left tarsometatarsus, 51.5 mm (2.03 in)-long and associated with the whole hallux, or digit I, and four intermediate phalanges. PVL-4048 was previously described as "Avisaurus sp." (see Avisaurus ). [4]
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