Diplodocus has always held a significant position in the hearts of dinosaur palaeontologists, as it was one of the very first genera to ever be formally recognised and described. Following, are some images and attempted reconstructions from Hutchinson (1917), and by comparison some excellent recent research by Taylor et al. (2009) on posture in Diplodocus carnegiei (or carnegii). I just figured it would be cool to show how mechanical interpretations and life reconstructions had changed over the years, since from dinosaurs were first mounted to now where more complex biomechanical modelling procedures are being utilised.
The following is a model reconstruction made from plaster based on the above skeleton. The tail rests on the ground, the neck is concave downwards and held-sub-horizontally, and the limbs are situated laterally to the trunk. Hutchinson (1917) explicitly says that despite this odd arrangement, Diplodocus did not crawl around on the ground like a lizard or crocodile.
Following the above reconstruction, there is a simple reconstruction of the pelvic girdle and hind-limb provided. The femur and the tibia/fibula are perpendicular, with the pes also perpendicular to that to rest on a substrate. It pretty much looks like the ischium gouged a furrow whenever the animal tried to walk in this reconstruction.
By comparison, more recent reconstructions are quite different. The following is just one of many illustrations by the talented Scott Hartman (follow @skeletaldrawing on Twitter). Note the distinct differences in posture: the legs are held vertically under (and slightly lateral) to the trunk, elevating the main body. Accordingly, the neck and tail both become more horizontal, acting as respective cantilevers with respect to the main body and the centre of gravity. Much more detail regarding stance and posture can be found on the wonderful SV-POW blog here, and in many formal publications.
Following on from reconstructions like above, the next step is to reconstruct the range of motion to discern possible ecological functions of various skeletal elements and domains. This has been done rather successfully by H. Mallison with Plateosaurus (Part 1 and Part 2). Hutchinson (1917) attempted a very rudimentary interpretation of this, as shown below.
Yeah, ok, it’s pretty basic. Some progress has been made in this field with sauropods however, notably that from Taylor et al. (2009) with regards to Brachiosaurus brancai, as shown below (edit: the Tendaguru Brachiosaurus brancai is now regarded as Giraffatitan brancai, Taylor, 2009; see comment below). Obviously Brachiosaurus is not Diplodocus, but it illustrates the point nicely.
Digital reconstruction is proving to be a pretty useful tool in imaging and interpreting life positions of dinosaurs and other extinct organisms. More recently, vertebrate palaeontologists, combined with mechanical modellers and zoologists have began to map muscles on to these digital skeletons using modern analogues and the ‘extant phylogenetic bracket‘ theory, to gain a significantly more detailed reconstruction and make more valid interpretations about extinct archosaur mechanics.
As computing technology has developed, palaeontologists have kept pace and are finding ever more elaborate methods to aid in understanding the mechanics, physiology, and ecology of extinct organisms. It’s an exciting field, with lots of promise for the future!
Note: I feel like a tit. Spent a whole year working/studying in the NHM London, and don’t have a single photo of the focal Diplodocus specimen there, Dippy. Oops.
Bates, K. T., Maidment, S. C., Allen, V. and Barrett, P. M. (2012) Computational modelling of locomotor muscle moment arms in the basal dinosaur Lesothosaurus diagnosticus: assessing convergence between birds and basal ornithischians, Journal of Anatomy, doi: 10.1111/j.1469-7580.2011.01469.x
Mallison, H. (2010) The digital Plateosaurus I: body mass, mass distribution and posture assessed using CAD and CAE on a digitally mounted complete skeleton, Palaeontologia Electronica, 13.2.8A
Mallison, H. (2010) The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount, Acta Palaeontologica Polonica, 55(3), 433-458
Taylor, M. P., Wedel, M. J. and Naish, D. (2009) Head and neck posture in sauropod dinosaurs inferred from extant animals, Acta Palaeontologica Polonica, 54(2), 213-220