Brachiosauridae incertae sedis, likely basal end of clade (cf. "Atlasaurinae")
Time horizon: Late Jurassic, Kimmeridgian to Tithonian epochs (~157-145 mya)
Length: ~15m (~50 ft.), perhaps more depending on maturity.
Probable mass: 17+ tons
An as-of-yet undescribed cousin of Atlasaurus [link]
from the Lourinhã formation in Portugal. This species has the same very slender, elongated arms but much bulkier hands, with very thick metacarpals resembling cinderblocks [link]
. The thumb claw is large but much closer to the ground that it would have been in Atlasaurus
, due to the longer thumb metacarpal. The specimen is on display in Bristol, England. [link]
A naturally occurring 3D cast of a sauropod hand from the same geological formation and locale may be from this same animal. [link]
. The shape of the cast indicates a very robust hand with the metacarpals arranged in a nearly circular form, with only the rearmost part of the hand hollowed out. This is common in macronarians, especially in brachiosaurs.
This still-unnamed brachiosaur is far closer to Atlasaurus
than anything else. It's also a younger species, and may represent a radiation of Atlasaurus
's descendants or close relatives into Portugal later in the Jurassic. Along with Atlasaurus
it occupies a basal position in Brachiosauridae, and probably forms a neat little Atlasaurinae with Europasaurus
as sister group. As for the mysterious sauropod's proportions, judging by the nearly identical arm segment ratios, they were probably not that different from Atlasaurus
, though the unnamed animal is a bit smaller. (If I were a certain field guide author, I might even be tempted to lump the two together, despite the unnamed animal being millions of years more recent and from a different continent and geological formation