Palaeontology to Palaeobiology
Interpretation of life, form, and locomotion from the fossil record
Indoor meeting
(co hosted with the North Eastern Geological Society and Northumbira OUGS)
Convened by Oliver Weeks and John Knight
University of Durham
Saturday 8th February
13:30 - 17:00
Non-members welcome!
Location:
Conference rooms ES 228/229 and ES 230, located on level 2 of the Earth Science building, University of Durham, DH1 3LE.
Schedule:
13.30 Welcome/ H&S briefing/ Intro to this meeting (Prof. Colin Waters, YGS President)
13.40 In the footsteps of dinosaurs: from tracks to locomotion (Prof. Phil Manning, Natural History Museum Abu Dhabi)
14.40 TBC (Dr Heda Agic, University of Durham)
15:15 Refreshments
15.45 TBC (Sam Cross, University of Liverpool)
16:20 Returning to water: how changing function shaped the jaws of whales (Oliver Weeks, Emanya Fossil Preparation and Conservation)
16:55 Closing remarks
Abstracts:
In the Footsteps of Dinosaurs: From Tracks to Locomotion
Prof. Phil Manning, Natural History Museum Abu Dhabi and University of Manchester
The study of both dinosaur tracks and biomechanics have taken some giant steps in the past 25 years, leading to a much better understanding of these organisms. Trace fossils remain a unique source of information, offering insight to the gait, posture and locomotion of dinosaurs but also to their behaviour and palaeoenvironments in which they thrived. The ‘sandbox’ of lab-based experiments has now been augmented by numerical modeling approaches that have sought to resolve the dynamic soil mechanics related to track formation but also the complex relationship between track-maker anatomy and limb kinematics. However, a disjunct still remains between dinosaur tracks and the musculoskeletal systems that generate traces, giving rise to significant debate. There is a frustrating rift between tracks and the specific identity of the track-maker, often creating poor fits between the two. More often than not… the shoe does not fit. But track preservation can still reveal important information on substrate consistency at the time of track formation. There has also been a long held assumption that many fossil tracks and trackways represent ‘surface’ features (at the sediment/foot interface). Track geometry and morphology (e.g. track length and track width, digit length, number of digits, interdigital angles) are based on what is visible on a bedding plane (occasionally weathering and erosion offers a helpful cross-section) and are usually recorded as 2-dimensional (2D) features. However, tracks are not 2D but often complex 3-dimensional (3D) structures. The tracks of dinosaurs and other extinct megafauna are truly the icebergs of the ichnological world, with a majority of each structure expressed below the ‘true’ track surface on which the animal walked. Although a surface track provides an opportunity to map a feature (another source of error when defining which surface landmark is to be measured), it is the relationship to underlying transmitted (‘stacked’) track surfaces that is the key to unlocking this 3D puzzle. Fossil tracks should be approached and visualised as 3D dynamic soil failure volumes and not simply as a single 2D page of a stratigraphic tome. Laboratory track simulations can provide some insight to the complex subsurface sediment deformation associated with track formation, but numerical modeling techniques have now established a valuable additional trail to interrogate the dynamics of track formation. The recovery of subsurface layers (physical and/or digital) provides valuable insight to track morphology relative to the true surface track. When compared with fossil tracks and the tracks of extant avian theropods (birds), an even more complete understanding of tracks and their formation can be undertaken. However, it must not be forgotten that extant birds utilise a knee-based f lexure system during locomotion that is quite different to many of their hip-based flexure dinosaurian kin. The tracks and trackways of dinosaurs are indeed common in the Mesozoic and can provide useful data on locomotor ability, but there are potential traps when it comes to speed estimates calculated from fossil trackway geometry. It is possible to under- or overestimate the speed at which an animal was traveling, if the foot length (used to calculate hip height when calculating dimensionless speed) is misinterpreted. This has the potential to change a slow walk to a sprint in some trackways. The huge variation in stacked-track dimensions within a single simulation 3D volume, relative to the ‘true’ surface track, also suggests that caution be exercised when using fossil tracks (and trackways) to calculate hip height, speed, organism age and population dynamics. The fossil tracks of dinosaurs and other extinct giants are without doubt useful to understanding past environments and locomotor ability, but care must be taken in dissecting the evidence else prey might end-up walking within the footprints of predators.
Returning to Water: How Changing Function Shaped the Jaws of Whales
Oliver Weeks, Emanya Fossil Preparation and Conservation
One of the most morphologically unique groups of mammals, whales are a remarkable example of evolutionary adaptation resulting from an extreme shift in ecology. This shift required alterations to almost every facet of their biology including diet, locomotion, reproduction, and sensory systems, and thus are a good model for how extreme selection can affect morphology. Perhaps the most extreme change that occurred was to the skull evolving from the 40 centimetre long skull of Pakicetus (comparable to their modern day relatives the cows) to over 5 metres long in blue whales and sperm whales, and changing even more dramatically in shape. Mandibular morphology is of key interest due to its relationship with feeding ecology, however, most work on the function of cetacean jaws is done in an isolated manner taking aspects such as the kinematics of suction or bulk feeding rather than talking a whole clade view of the jaw function. This research brings together form and function through morphospaces and adaptive landscapes, using elliptical Fourier analysis (EFA) and finite element analysis (FEA) to quantify the functional changes related to mandibular evolution associated with an aquatic transition. The analyses show that the transition from terrestrial to aquatic ecologies incurs a trade-off losing jaw strength in favour of increasing the jaw’s rotational efficiency. Once restricted to this aquatic lifestyle, the morphology of whale jaws is largely dictated by feeding strategy as the medium of water allows for unique modes such as suction feeding, with specific prey types being less influential. Somewhat unexpectedly, the ecological transition does not incur a significant morphological constraint.