Preservation of three-dimensional anatomy in phosphatized fossil arthropods enriches evolutionary inference

  1. Achim H Schwermann  Is a corresponding author
  2. Tomy dos Santos Rolo
  3. Michael S Caterino
  4. Günter Bechly
  5. Heiko Schmied
  6. Tilo Baumbach
  7. Thomas van de Kamp  Is a corresponding author
  1. University of Bonn, Germany
  2. Karlsruhe Institute of Technology, Germany
  3. Clemson University, United States
  4. State Museum of Natural History Stuttgart, Germany
7 figures, 1 table and 2 additional files


Comparison between the fossil Onthophilus intermedius (ADG) and EtOH-fixed (BEH) and air-dried (CF , I) specimens of O. striatus.

Slices of tomographic volumes showing head region (AC), thorax (D–F) and abdomen (G–I). ae = aedeagus; ag = accessory gland; bpae = basal part of aedeagus; hg = hindgut; m = musculature; ml = median lobe; mr = muscles remnants; mscx = mesocoxa; msf = mesofemur; mst = mesotibia; mt = muscle tissue; mtcx = metacoxa; mtf = metafemur; mtt = metatibia; pcx = procoxa; sph = spherical particle; sm = stony matrix; t8 = 8th abdominal tergite; t9 = 9th abdominal tergite; t10 = 10th abdominal tergite; te = tentorium; tr = trachea.
Surface renderings of the eight Onthophilus intermedius specimens.

Note the unique encrustation of F1994.
Digital reconstruction of the fossil.

(A) Photograph of Onthophilus intermedius (F1994) ventrally embedded in a stony matrix. (B) Digital reconstruction showing fossilized beetle (green) and matrix (brown). (C) Beetle digitally isolated from the stone, revealing well-preserved morphology hidden by the matrix. (D) Perspective view of the fossil showing parts of exoskeleton, tracheal network, alimentary canal and genitals. (E, F) Comparison of the male genitals of the extant O. striatus (E) and the fossil O. intermedius (F); outer sclerites cut to reveal internal anatomy. See Supplementary file 1 for an interactive version of the 3D reconstruction.
Coxa-trochanteral joints.

Comparison of the joints (cut) of the left mid- (AB) and hind leg (CD) of Onthophilus striatus (AC) and O. intermedius (BD), showing coxae (green) and trochanters (yellow).
Digital endocast of Onthophilus intermedius (specimen F1994).

A digital endocast (AB) artificially created from tomography data resembles the shape of the other fossils (Figure 2) much closer than the original surface of the beetle (CD) hidden by the stony matrix.
Strict consensus tree.

The analysis places Onthophilus striatus within a lineage of Nearctic and far-eastern Palaearctic species (red), while O. intermedius is a member of a separate Holarctic lineage (blue). Four internal (purple) and three external (orange) unambiguous synapomorphies supporting their respective placements are mapped onto the cladogram - Onthophilus striatus group: Character 22:2, mesoventrite wide and short; 30:1, pygidial median carina absent; 35:2, tegmen of aedeagus abruptly downturned apically. O. intermedius group: 29:2, pygidium laterally impunctate; 36:2, tegmen of aedeagus abruptly narrowing apically; 40:2, lateral halves of eighth sternite large and nearly meeting at midline; 41:2, stem of spiculum gastrale broad throughout its length.
Appendix figure 1
Morphological characters visible in specimens other than F1994.

(A) Dorsal view of F1951, showing elytral carinae and foveae. (B) Posterolateral view of F1997, showing propygidial and pygidial carinae. (C) Posterior view of F1951. (D) Anterior view of F1995. (E) Valvifer and coxite of female ovipositor.


Table 1

Notes on the fossil Onthophilus intermedius specimens from Quercy and their preservation.
IDInternal structures preservedNotes
F1951some sclerites (incl. coxa-trochanteral joints) and tracheaethe only specimen depicted by Handschin (1944); but not explicitly designated as holotype
F1992some sclerites and small tracheaehead, prothorax missing
F1993some sclerites (incl. coxa-trochanteral joints)head, pygidia missing; elytra partly abraded
F1994most sclerites, muscle parts, tracheae, parts of alimentary system, large parts of male genitalsthe only specimen of the collection that is ventrally encrusted by a stone matrix
F1995some sclerites, parts of male genitalshead present; abdomen deeply abraded dorsally
F1996some scleriteshead, prothorax missing
F1997some sclerites, remains of muscles below the elytrahead, prothorax partly abraded
F1998some sclerites (incl. coxa-trochanteral joints), parts of female genitaliahead, prothorax partly abraded

Additional files

Supplementary file 1

Interactive 3D reconstruction of Onthophilus intermedius specimen F1994.

Click on the figure to start interactive 3D view; switch between views by using the menu (Adobe Reader 8.1 or higher required).
Source code 1

Nexus code for character matrix.

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  1. Achim H Schwermann
  2. Tomy dos Santos Rolo
  3. Michael S Caterino
  4. Günter Bechly
  5. Heiko Schmied
  6. Tilo Baumbach
  7. Thomas van de Kamp
Preservation of three-dimensional anatomy in phosphatized fossil arthropods enriches evolutionary inference
eLife 5:e12129.