Computed tomography recovers data from historical amber: an example from huntsman spiders

Area of Science:

• Paleontology
• Arachnology
• Paleoarthropology

Background:

• Fossil spiders in Baltic amber, particularly Ocypete crassipes, are difficult to study due to dark, oxidized amber and lack of detailed descriptions.
• Previous assignments to the genus Heteropoda and the family Sparassidae were based on limited evidence, making the fossil an equivocal record.

Purpose of the Study:

• To re-examine the problematic fossil spider Ocypete crassipes using advanced imaging techniques.
• To confirm the taxonomic placement of O. crassipes within the family Sparassidae and the subfamily Eusparassinae.
• To demonstrate the utility of computed tomography (CT) in resolving taxonomic ambiguities in fossil specimens.

Main Methods:

• Application of phase contrast enhanced X-ray computed tomography (CT) to fossil specimens of Ocypete crassipes from Eocene Baltic amber.
• Detailed analysis of fine morphological structures including eye arrangement, cheliceral dentition, leg spination, and claws.
• Comparison of fossil morphology with extant spider taxa for taxonomic classification.

Main Results:

• CT imaging revealed exquisite morphological detail previously obscured by the amber matrix.
• The fossil spider exhibits characters confirming its placement within the family Sparassidae and subfamily Eusparassinae.
• The species is reclassified as Eusparassus crassipes (Koch and Berendt 1854) comb. nov., representing a bona fide huntsman spider.

Conclusions:

• Computed tomography (CT) is a powerful tool for taxonomic revision of poorly preserved fossil specimens.
• The re-examination of Ocypete crassipes validates its status as an early Eusparassinae huntsman spider.
• This study highlights the importance of advanced imaging in understanding spider evolution and fossil records.