Trackways Produced by Lungfish During Terrestrial Locomotion.

Area of Science:

• Paleontology
• Ichthyology
• Vertebrate Paleontology

Background:

• Aquatic vertebrates venturing onto land produce traces that may be overlooked or misidentified in the fossil record.
• Previous models for tetrapod locomotion often used extant fish species that differ significantly from Devonian fishes.
• While fish locomotion is studied, the specific production of trackways by terrestrial-moving fishes is less understood.

Purpose of the Study:

• To investigate and document the terrestrial locomotion and trackway production of the African lungfish (Protopterus annectens).
• To compare lungfish trackways with fossil traces, particularly those interpreted as early tetrapod footprints.
• To enhance the understanding of potential fossil evidence for vertebrate terrestrialization.

Main Methods:

• Recording the terrestrial locomotion of a 35 cm African lungfish on compliant sediment.
• Analyzing the morphology and pattern of the impressions left by the lungfish during its movement.
• Comparing the observed traces with known fossil trackways.

Main Results:

• African lungfish achieve terrestrial locomotion by planting their head and pivoting their trunk.
• The primary traces are formed by the impact of the head, specifically the upper and lower jaws, creating alternating left-right semi-circular impressions.
• Body and fin traces are minimal, with head impacts resembling some fossil traces interpreted as footprints.

Conclusions:

• The study provides a model for understanding how aquatic vertebrates, like lungfish, may create fossilizable traces on land.
• The unique head-based trackway of Protopterus annectens offers a potential analogue for certain fossil footprints.
• Further research on extant terrestrial fish trackways is crucial for accurately interpreting the fossil record of vertebrate terrestrialization.