Plesiosauria

Ricqlès, Armand de, Taquet, Philippe & Buffrenil, Vivian de, 2009, “ Rediscovery ” of Paul Gervais’ paleohistological collection, Geodiversitas 31 (4), pp. 943-971 : 951-955

Plesiosauria

20. “Plesiosaure. Apophyse épineuse de vertèbre dorsale.” Pencil number: 986, ink label: 1938 no. 627 ( Fig. 2B ).

Description. Bone tissue is observed on a 20 × 5 mm surface. This section is of fairly good technical quality and allows detailed observations. The preserved free surface of the bone is flat and formed by a very thin cortex which likely experienced subperiosteal resorption. This cortex has the same histological structure as the inner trabeculae which merge with it locally. Inside the bone, the tissue is cancellous, formed of very irregular trabeculae. These trabeculae are of endochondral origin, as evidenced by the presence in their core of many island of calcified cartilage, with their clusters of large chondrocytes lacunae. The globular mineralisation of the cartilage matrix is also conspicuous, as well as globuli ossei localized at the interface between bone and cartilage (cf. Buffrénil et al. 1990).

Comments. The resorbing trabeculae forming the cortex retain an endochondral component. This structure is comparable to the surface of long bone metaphyseal regions which have to reduce their outer diameter (modeling) during the growth in length of the bones, so that the overall morphology of the bones can be maintained while metaphyseal regions are sequentially relocated ( Enlow 1963).

21. (N-5) – Pliosaur.Ink label: “Plesiosaur Plesiosaur (the two words striked of) maxill. inf. Pliosaur”. Anat. Comp. 1878. Pencil label: 987.

Description. A cross section of a rather compact bone fragment (jaw), about 17 mm long and 6 mm maximal width, in part contained in matrix. The preservation is fair, although the balsam has badly shrunk and cracked below the cover plate. The subperiosteal bone tissue shows incorporation of new vascular canals, Sharpey’s fibers and “growth cycles”. The osseous tissue shows evidence of post mortem degradation, suggesting that the bone was stranded on shore before ultimate fossilization. The inner bone is extensively converted into Haversian systems and contains large “marrow” sinuses, one tooth socket and some tooth material. However it has entirely experienced diagenesis and no dental tissue structure remains.

Comments. A striking artifact is provoked locally by the schrinken balsam, that displays appearance of a globular tooth with an “onion sheets” structure under low magnification.

22. (N-6) – Pliosaurus . Ink label: “ Pliosaurus grandis du Havre , mach. Inf-re.” Anat. comp. (no date, no number).

Description. A longitudinal (oblique) section in fairly dense bone, about 10 × 7 mm. The tissue

has numerous elongate periosteocytic lacunae. It contains numerous vascular canals, roughly parallel to each others, with some evidence of secondary reconstruction around them. A more cancellous region with some irregularly shaped sinuses carved into dense secondary tissues corresponds to the endosteal margin.

Comments. Superficial (sub periosteal) bone layers do not seem to be preserved in the section.

DINOSAURIA

23. (N-7) – Iguanodon . Ink label: “Fossil bone Iguanodon ”. No pencil number. No date, with the label “– C. M. TOPPING –” appearing twice in circles on red and gold paper covering the top of the glass slide ( Fig. 1A ).

Description. A 8 × 8 mm cross section in coarse cancellous bone. The section is rather thick but the bone structure can be deciphered. The bone trabeculae are irregular and thick, with small marrow spaces between them. The bone tissue is secondary and remodeled. It appears mostly endosteal in origin.

Comments. One of the early thin sections of British origin in P. Gervais’ collection, and one of three with the same, careful technical setting under red and gold paper. The material should come from an Iguanodon Mantell, 1825 fragment from England antedating the Bernissart discovery; it is so impossible that this specimen comes from the Belgium material. However, the origin of this specimen is not precisely known ( England, Isle of White?).

24. “ Iguanodon fémur”. Ink label: 1938 no. 620, MNHN 1875 (figured in Taquet 2001).

Description. A cross section probably in the external cortex from the shaft of a long bone. Bone tissue is entirely primary in structure. The section is polluted by abrasive grains but the structures can nevertheless be observed. The bone tissue with a dense, homogeneous and regular vascularisation organized as primary osteons, is typically laminar to sub-plexiform.The bone surface, as preserved, shows no evidence of an external fundamental system or a decrease in appositional rate. However it might not represent the natural subperiosteal surface of the bone. No lines of arrested growth, or Haversian substitution are clearly visible.

Comments. The structure suggests an immature, actively growing individual.

25. (N-8) – Iguanodon . Ink label: “ Iguanodon femur”. Mus. Nat. Hist. Nat. 1876. No numbers. ( Fig. 2C ).

Description. An excellent thin section in compact bone, about 10 × 9 mm, plus some additional fragments. The main part of the section is a cross section through a massive cortical bone entirely formed by primary (periosteal) bone tissue of laminar to sub-plexiform types. Only a few vascular canals have experienced Haversian reconstruction.Five small additional fragments under the same cover slip figure the same tissue, but cut tangentially, parallel to the bone surface. They show three complex (and difficult to interpret) interwoven components: 1) the fibrous component of periosteal origin; 2) the lamellar component of the primary osteons (endosteal component); and 3) the vascular component locally appearing as a reticulum (e.g., Ricqlès 1972: figs 6, 7).

Comments. The structure, similar to section 24 (see above), should originate from the same material. It also suggests a fast, massive, almost continuous new bone apposition in a presumably juvenile to half grown individual. This thin section, again, raises the issue of the origin of the material. It looks to have been processed in Paris, along most others from Gervais’ collection, possibly by E. Bourgogne or C. March- and (although no label suggests this). If so, and if the material indeed belongs to Iguanodon , it should have come from a fragment sent from England. An alternative is that the material comes from Southern France (see below) and was labelled Iguanodon by comparison with other sections, published or not.

26. (N-9) – Rhabdodon. Ink label: “Rhabdodon, vertèbre de Villeveyrac” Mus. Nat Hist. Nat., Anat. Comp. 1876. ( Fig. 2D ).

Description. Two small irregular fragments under a square coverslip. The bone tissue is mostly cancellous, and only one small region seems to agree with a bone cortex of primary (periosteal) origin. This cortex is densely vascularized by up to five rows of primary osteons organized into a vaguely laminar pattern. The spongiosa starts abruptly in the deep cortex, which is dissected by large marrow cavities. The endosteal trabeculae are very remodelled. The whole bone experienced extensive post mortem erosion by boring organisms.

Comments. Taquet (2001), dealing with early discoveries of Dinosaurs from Southern France, notably by the geologist Philippe Matheron, commented the likely occurrence of Rhabdodon Matheron, 1869 at Villeveyrac (Herault) ( Taquet 2001: 620), as well as Matheron’s relationships with Paul Gervais (cf. Gervais 1877 in Taquet 2001) about those dinosaurian remains. This thin section confirms their relationships.

27. (N-10) – Dinosaur indet. Ink label: “ Reptile de la Nerthe (Matheron) marne (?) inf. Eugène Bourgogne, préparateur à Paris”. No date, no pencil number ( Fig. 1A ).

Description. A thin section of triangular shape, about 10 × 6 mm. Most of the section is formed by a dark matrix, containing bony fragments. The tissue, sectioned longitudinally or obliquely, is highly birefringent under crossed nicols. It is an intensively reconstructed bone tissue that may be Haversian or secondary endosteal.

Comments. From La Nerthe tunnel, Matheron described fragments of both “ Hypselosaurus ”, a Sauropod, and Rhabdodon, an Ornithopod (cf. Taquet 2001: 614-615). The secondary nature of the tissue would agree with a Dinosaurian origin. The section likely comes from the material given by Matheron to P. Gervais in 1876 which thus would have contained not only eggshells fragments ( Taquet 2001: 616) but also bone fragments.

28. (N-11) – Dinosaur indet. Ink label: “Dinosaurien? Vertèbre du Garumnien de Esperaza par

Mr. Leymerie. Museum d’Hist. Nat. Anat. Comp. 1876” ( Fig. 1B ).

Description. A small bone fragment, about 7 × 5 mm in longitudinal section. The tissue is highly birefringent throughout. A small region may correspond to the deep primary cortex, with a few Sharpey’s fibers and rather abundant anastomosing vascular canals sectioned longitudinally. However, most of the section is secondary endosteal and would form the external part of a rather dense spongiosa.

Comment. Again, this section does not bear much “diagnostic” characters but the structure could generally agree with a dinosaurian origin. Taquet (2001: 620) quotes the letter dated July 1877 of Mr. Leymerie to Paul Gervais discussing the bone fragments from Fa and Esperaza (Aude) from which this section comes.

MAMMALIA “Edentates”, Xenarthra Glyptodontoidea

29. Glyptodon “cubitus”. Pencil number: 48, ink label: 1938-612. Anat. Comp. 1878.

Description. A bone cross section, semi-circular in shape of 23 mm diameter. Although tissue preservation is poor overall, it allows precise microanatomical and histological analysis, at least locally. Contrast between what are usually a central cancellous region opposed to a dense cortex is low here. The cortex is locally highly cancelous via large radial, circular and longitudinal canals. Conversely the inner bone tissue is rather dense, with thick bony trabeculae and relatively small marrow spaces. A part of the cortex is primary, with a plexiform vascular network. Large vascular canals with incipient osteonal deposition open under at the surface of the cortex. This suggests that sub-periosteal accretion was still actively proceeding when the animal died. At some distance from the surface, circular vascular canals experience resorption. Inner bone is formed by complex, remodelled endosteal trabeculae rather than typical Haversian systems.

Comments. The section suggests an immature, fast growing bone, perhaps exposed to peculiar biomechanical demands for a land dwelling mammal.

30. Glyptodon “cubitus”. Pencil number: 48, ink label: 1938-612. Anat. Comp. 1878.

Description. A longitudinal section (12 × 10 mm) in compact bone. The section agrees with the description above. It documents the high vascularisation of the periosteal bone tissue via longitudinal, circular and some radial canals, and also the development of Sharpey’s fibers.

31. Glyptodon “cubitus”. Pencil number: 48, ink label: 1938-612. Anat. Comp. 1878.

Description. A small longitudinal section (4 × 10 mm in two parts) in compact bone.The natural subperiosteal surface of the bone is exposed on one side of the section, while the endosteal (perimedullar) region is exposed on the other side. What can be deciphered is consistent with the preceding section.

32. Glyptodon “cubitus”. No pencil number. Ink label: Anat. Comp. 1878.

Description. A small longitudinal section (7 × 9 mm) in compact bone. In this better preserved section, the primary structure of the densely vascularized bone cortex is easily observed.

33. Glyptodon “cubitus”. No pencil number. Ink label: Anat. Comp. 1878.

Description. A larger longitudinal section (14 × 9 mm) in compact bone.No primary bone at the subperiosteal surface is observed. The section is entirely composed by the inner secondary bone tissue.The stout longitudinally organized endosteal trabeculae leave between them only relatively small marrow spaces.

Figures

FIG. 2. — A, Ichthyosaur tooth (section no. 19), cross section in ordinary transmitted light, conspicious growth marks (arrow heads) are present in the dentine; B, neural spine of a plesiosaur (section no. 20), cross section in ordinary transmitted light, the cores of the trabeculae still contain remnants of calcified cartilage matrix (arrow); C, Iguanodon Mantell, 1809 femur (section no. 25), cross section in ordinary transmitted light, the bone tissue is of the laminar type (lb); D, section of an undetermined bone from Rhabdodon Matheron, 1869. (section no. 26), the deep cortex (at the lower right corner of the photo) is extensively eroded and broad resorption bays (asterisk) are created; E, Megatherium Cuvier, 1796 tooth (section no. 36), a and b designate respectively tissues a and b, as described in the text, the sparse remants of tissue c are not visible on this picture, cementing line (cl), vascular canals (vc); F, humerus of a bradypoid (section no. 38), cross section in ordinary transmitted light, primary grossly lamellar cortex (plc), Haversian bone (hb). Scale bars: A, 0.55 mm; B, 0.36 mm; C, 0.85 mm; D, 1 mm; E, 0.20 mm; F, 0.60 mm.

FIG. 1. — A, General aspect of the ground sections in Paul Gervais’ collection; above: section 76 x 26 mm (a format still in use today) from a dinosaur bone (so called “reptile de la Nerthe”) made in Paris by E. Bourgogne (section 27 [N-10]), below: section from an Iguanodon Mantell, 1809 bone made in Great Britain (section 23 [N-7]). The latter section is protected by a cover of strong paper; B, detail of the kind of information written on the labels.This section (section 28 [N-11]) is supposed to be from a dinosaur;C, tooth-like organ of Lamna Cuvier, 1816 (section no. 3), longitudinal section in ordinary transmitted light, a1-3 and b refer to the two main tissue types observed in this section (see description in text); D, Archegosaurus latirostris Jordan, 1849 (i.e. juvenile Archegosaurus decheni Goldfuss, 1847) tooth (section no. 4), cross section in ordinary transmitted light, globular dentine (gd, dark peripheral layer) is close to the tooth surface; E, section of a “cranial bone” of Labyrinthodon Owen, 1842, a synonym of Mastodonsaurus Jaeger, 1828 from Wurtemberg (section no. 7), ordinary transmitted light, a few vascular canals and lignes of arrested growths (arrows, lines of arrested growth) can be observed;F, section of the “temporal scale” of Labyrinthodon from Stuttgart (section no. 9), polarized transmitted light (crossed nicols), the tissue is finely lamellar. Scale bars: A, 26 mm; B, 13 mm; C, 0.55 mm; D, 0.32 mm; E, 1 mm; F, 1.2 mm.