Pronunciation: BO-nuh-TIE-tuhn
Meaning: Bonaparte Giant
Author/s: Martinelli and Forasiepi (2004)
Synonyms: None known
First Discovery: Río Negro Province, Argentina
Discovery Chart Position: #542
Bonatitan reigi
Once upon a time, the bones of Bonatitan reigi were considered more slender than those of fellow saltasaurines Saltasaurus and Neuquensaurus. Among all saltasaurines, they most closely resembled Rocasaurus—though the only fossils available for direct comparison were thighbones, and even those differed in the shape of the distal condyle (the bulbous end that forms the knee joint with the shin condyle).
In Rocasaurus, the thigh and shin condyles are similarly sized, but in Bonatitan—and, funnily enough, Saltasaurus and Neuquensaurus—the thigh condyle is noticeably smaller. However, Bonatitan isn't a saltasaurine. Not anymore.
In 2014, Salgado and colleagues re-examined the Bonatitan bone pile and realised that (1) several bones had been misidentified, (2) what was initially thought to be two individuals (MACN-PV RN 821 and MACN-PV RN 1061) was actually five, and (3) the holotype, which should be a single individual for name-carrying purposes, contained parts from at least three. After some anatomical triage and specimen reassignment, the holotype was pared down to a well-preserved braincase, and a tweaked analysis recovered Bonatitan as a non-saltasaurine titanosaur.
In 2014, Salgado and colleagues re-examined the Bonatitan bone pile and realised that (1) several bones had been misidentified, (2) what was initially thought to be two individuals (MACN-PV RN 821 and MACN-PV RN 1061) was actually five, and (3) the holotype, which should be a single individual for name-carrying purposes, contained parts from at least three. After some anatomical triage and specimen reassignment, the holotype was pared down to a well-preserved braincase, and a tweaked analysis recovered Bonatitan as a non-saltasaurine titanosaur.
(Reig's Boneparte Giant)Etymology
Bonatitan is derived from "Bonaparte" (for Argentine palaeontologist José Fernando Bonaparte, who directed the field trips that discovered its remains) and the Greek "titan" (giant).
The species epithet, reigi, honours Osvaldo Reig for his contributions to South American palaeontology.
Discovery
The remains of Bonatitan were discovered in the lower member of the Allen Formation (Malargüe Group) at Bajo de Santa Rosa, Río Negro Province, Argentina, by José Bonaparte-directed Museo Argentino de Ciencias Naturales field trips during the summers of 1991, 1992 and 1994.The holotype (MAGN-PV RN 821, aka "Individual C") is a well-preserved braincase. Initially, this specimen was thought to include many additional fossils, but a 2014 review determined that those remains actually belonged to several distinct individuals. Likewise, referred material (MACN-PV RN 1061), originally thought to be a smaller second individual, was found to represent multiple individuals too. In total, five individuals have now been identified—labeled "A" through "E"—including some bones that were previously undescribed or lacked catalogue numbers. • Individual A
Originally part of the holotype (MAGN-PV RN 821):
A partial right shin, one foot bone, one tail vertebra
Originally referred to a second specimen (MACN-PV RN 1061):
Two hand bones (one of which was misidentified as a forearm bone), one complete and two partial foot bones • Individual B
Originally part of the holotype (MAGN-PV RN 821):
A partial back vertebra, two neural arches, a rib, a left shin and calf, an ankle (misidentified as a heel) and two thighs.
Originally referred to a second specimen (MACN-PV RN 1061):
A braincase (20% smaller than the holotype) and a partial neck vertebra. • Individual C
The holotype braincase. • Individual D
Originally part of the holotype (MAGN-PV RN 821):
An upper arm bone.
Originally referred to a second specimen (MACN-PV RN 1061):
A thigh, a shin and an ankle.
No previous catalogue numbers:
Many foot bones, mostly fragmentary, and at least six chevrons.
Based on thigh size, Individual D is 20% smaller than Individual B. • Individual E
Originally referred to a second specimen (MACN-PV RN 1061):
Two footbones, 35% smaller than those of Individual A.
No previous catalogue numbers:
One tail vertebra.
Preparators
R. Vacca of the Museo Paleontológico Egidio Feruglio (MEF) and M. P. Isasi of the Museo Argentino de Ciencias Naturales (MACN).
