New perspectives on body size and shape evolution in dinosaurs.

Area of Science:

• Paleontology
• Biomechanics
• Evolutionary Biology

Background:

• Dinosaur body shape and size diversity influenced their success.
• Accurate body mass and form quantification is crucial for studying dinosaur biology and evolution.
• Previous body mass estimates often relied on subjective methods and artistic inference.

Purpose of the Study:

• To develop a quantitative approach for estimating dinosaur body mass and segment properties.
• To systematically constrain body segment volumes using scaling relationships between fossilized hard tissues and extant soft tissues.
• To investigate mass distribution and body proportions in dinosaurs based on anatomical data.

Main Methods:

• Utilized skeletal models of 52 non-avian dinosaurs from major clades.
• Applied skeletal to soft tissue volumetric scaling factors derived from CT scans of extant sauropsids.
• Estimated body segment mass properties and total body mass.

Main Results:

• Estimated body masses ranged from under 200g to over 60 tonnes.
• Inferred that many dinosaurs were heavier than previously estimated due to larger soft tissue envelopes.
• Reconstructed mass distribution and body proportions, revealing variations in posture and locomotor dynamics across clades.

Conclusions:

• The new method provides a more reliable estimation of dinosaur body mass and form.
• Findings suggest significant variability in skeletal to soft tissue volume ratios among dinosaur clades.
• Reconstructed mass distribution supports hypotheses on dinosaur posture, function, and behavior, including decreased locomotor performance with increased size.