Inside Dinosaur Bones: A Discussion with Laughing Bear Torrez and Aaron Gilmore

Inside Dinosaur Bones: A Discussion with Laughing Bear Torrez and Aaron Gilmore

Join Laughing Bear Torrez and Aaron Gilmore in a fascinating discussion on the wonders hidden inside dinosaur bones, with a focus on the timeline of dinosaur bones and a comparison of Iguanodon bones to bones of modern animals.

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About Inside Dinosaur Bones: A Discussion with Laughing Bear Torrez and Aaron Gilmore

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1. Inside Dinosaur Bones Discussion By: Laughing Bear Torrez Aaron Gilmore

2. Dinosaur Bone Timeline Comparison of Iguanodon bones to bones of modern lizard. Osteocyte lacunae observed. Haversian canals identified in sauropod, illustrated osteons in dorsal spine of Hylaeosaurus. Named Dinosauria, vertebrae of Cetiosuarus used to illustrate dense laminar or plexiform tissue. 1849 John Thomas Quekett 1850 Gideon Mantell 1859 Sir Richard Owen

3. Microstructure Timeline Illustrated Knochen koperchen in many dinosaurs, established primary and secondary vascular canals in compact bone. Dinosaur bone unlike lamellar zonal bone in extant reptiles, more like mammals and birds Identified zonal bone in sauropod dinosaur. (Cambell, 1966) Clarification of Terminology 1907 Adolf Seitz 1960s Armand de Ricqles 1980s Robin Reid

4. Work by Chinsamy (1980s ) Comparative changes in the ontogeny of different dinosaurs Extant Phylogenetic Bracketing ? extant sharks, crocodiles, birds, non-mammalian synapsids, and pterosaur bones and teeth.

5. Interesting Contemporary Studies Horner & Padian w/ Ricqules bone microstructure of: Hypacrosaurus Maiasaura peeblesorum Confuciusornis Erickson & Tumanova Growth series of femora of Psittacosaurus Rigby-Schweitzer Search of Biomolecules Rimbolt-Baly Calculated daily bone depositional rates

6. Controversy Rensberger & Watabe (2000) collagen fibers and canaliculi are differently organized in different dinosaur lineages: Ornithomimid arrangement similar to birds Ornithiscian similar to mammals Chinsamy highly variable orientation due to age, rate, and sectioning of bone Need more extant research

7. Types of Bone in Dinosauria Compact (cortical) Primary periosteal bone Accretionary Haversian bone Metaplastic bone Cancellous (spongy) Endochondral primary Secondary reconstructed Dental Cavernous Flat bone - diplo

8. Compact Bone Tissues Channels house blood vessels and connective tissue Starck and Chinsamy (2002) only 20% of channels occupied by blood vessels. Figure 4.1

9. Dinosaur Zonal Bone de Ricqles (1974, 76) fibrolamellar with secondary haversian reconstruction Campbell (1966) described annulate structures in cortical dinosaur bone Robin Reid (1981)- lamellar-zonal bone in pelvis of sauropod - widespread Figure 4.3

10. Zonal Bone Structure Alternating fibrolamellar bone and Lines of Arrested Development (LAGs) LAG pause in osteogenesis Annuli more slowly formed bone Could be seasonal Plate 5A

11. Sexual Maturity Decrease in the width of zones (after X) Chinsamy is not convinced irregular width of growth rings Figure 4.4

12. Caution Growth rings could be caused by other factors (such as drift). Figure 3.1 Different bones in skeleton have different morphology Best in long bones Negligible remodeling in nonweight-bearing bones Shape of bone, lifestyle adaptations, and age are important considerations Tyrannosaurus fibula with 17 rings and dense haversian bone remodeling.

13. Skeletochronology If you have increasing number of growth rings with increasing size: Syntarsus Troodon Massospondylus Psittacosaurus Most likely periodic interruptions directory/drawing/Syntarsus.jpg

14. Sexual Dimorphisms Both azonal and zonal bone (Dryosaurus letterwvorkbecki) found Barosaurus (Sander, 2000) found bones with both azonal and zonal microstructure from the same dinosaur. Could be a sexual dimorphism Small sample size taxonomic differences? Cynagnathus & Diademodon (skull) Other sauropods are type A Apatosaurus (Rogers) Richly vascularized reticular and laminar bone

15. Outer Circumferential Layer Formed in mammals and birds with determinate growth strategies Avascularized With/without growth lines Ceratosaurus (Reid, 1996) Many do not have OCL Dinosaurs grew throughout their lives (de Ricqules) Largest Dinosaurs not sampled

16. Haversian Bone Secondary, dense haversian bone Well developed sauropod bones

17. Secondary Reconstruction Increases with age among modern vertebrates Dryosaurus small femur already had completely formed secondary osteons Similar to a mammal (dogs seven weeks/humans eight months) Occurs in the inner parts of cortical bone near the medullary cavity Unremodeled bone is stronger better on the outside (periosteal region)

18. Inner Circumferential Layer Medullary lining bone (Reid, 1996) Following medullary enlargement deposits of lamellar bone ICL is found in many dinosaurs Iguanodon, Rhabdodon Distinctive external boundary tide line Marks resorption also in ICL

19. Compacted Coarse Cancellous Bone Results from the endosteal infilling of cancellous spaces, and indicates that the bone was located at the metaphysis in early ontogeny and was relocated to the diaphysis as the growth and remodeling occurred. Chinsamy has documented compacted coarse cancellous bone in Dryosaurus femora distal and proximal ends.

20. Compacted Fine Cancellous Bone Fine cancellous bone is compacted into compact bone. Although not observed in dinosaurs spicules of calcified cartilage are present in the resulting compact bone of Mesozoic mammals and white rat cortical bone.

21. Summary of Compacta Several types of endosteally and periosteally compact bone occur throughout the skeleton, in different bones and even at the level of a single bone cross section. Even similar tissue types will have variation. Sharpeys fibers are collagen fibers responsible for securing a tendon or ligament to the outer fibrous layer of periosteum and to the outer circumferential and interstitial lamellae of bone. The number of Sharpeys fibers vary between similar tissue types.

22. Cancellous Bone in Dinosaurs In long bone is located internally around the medullary cavity and at the proximal and distal end. Called diplo in flat bones. Types of Cancellous bone in dinosaurs: Endochondral primary bone, secondary reconstructed cancellous bone, dental bone and cavernous bone.

23. Cancellous Bone: Endochondral Bone Forms by endochondral ossification that replaces cartilage. Described in Iguanodon centra; epiphyses of Iguanodon, Hypsilophodon, Dryosaurs ; limb bones of Valdosaurus; Nqwebasaurs femora; and in Maiasaura. Rapid endochondral bone formation is inferred if islands of calcified cartilage are present in trabeculae, observed in many adult dinosaurs.

24. Cancellous Bone: Secondary Resorption of primary cancellous bone of trabeculae walls with lamellar replacement of a cancellous texture; this reconstructed cancellous bone is the major type of dinosaur cancellous bone except at the metaphysis. Distinguished by tide lines of bone resorption in the trabeculae. Resorption of primary compact bone from vascular channels without redeposition also results in secondary cancellous bone transformation. Also well described in dinosaurs .

25. Other Bone Types: Metaplastic When tendon or ligament tissue undergoes ossification to become mineralized and preserved the resulting bone is considered metaplastic. Osteoderms were once considered metaplastic but new theories treat it separately.

26. Other Bones: Osteoderms Osteoderms consisit of a variety of bone tissues, and can vary in the same dinosaur. Example: stegosaur dorsal plates and a lateral ossicle of the body. A single Stegosaur dorsal plate osteoderm was observed to vary in microstructure from the apex to the base. Periphery of compact bone tissue in thin sheets cancellous bone in the center sparely vascularized lamellar zonal bone Haversian systems Haversian coreing to cancellous spaces, also reconstructed Sharpeys fibers within primary cortical bone. The orientation pattern from Sharpeys fibers of the dorsal plates was used as evidence of a vertical orientation along the dorsal midline. So is it more likely that the dorsal plates functioned as armor or some form of thermoregulation?

27. Other Bones: Osteoderms Recent Studies of Osteoderms have suggested non metaplastic origins: Riqcles found ankylosaur dermal ossifications that were button-like having dense parallel fiber bundles, abundant Sharpeys fibers, poor vascularization. The fibrillar mesh size and diameter increase radially which is contrary to metaplastic formation and suggests de novo formation of the ossicles. Salgado found titanosuar bony dermal plates characterized as non-osteoderms. He suggested the plates were true bone originating from epiphysis of neural spines, similar to cartilaginous structures in reptiles that can undergo ossification.

28. Pathological Bone Diffuse idiopathic skeletal hyperostosis (DISH)- calcification of ligament and tendon attachments. Frequent in dinosaurs along spinal longitudinal ligaments parallel to the vertebral column long axis; keeps vertebral column aligned, possibly permitting the tail to be high off the ground and stabilizing lateral movement.

29. Pathological Bone Although most pathologies observed via X-rays and morphology some other histological identifications are: Campbells hyperstotic periosteal outgrowths (recactive bone), which are honeycomb-like in structure and exhibit some communication. Osteoporotic bone observed in Apatosaurs scapula and Camarasaurus limb bone. Common are healed fracture calluses. It was observed that 1% of ceratopsians and hadrosaur have midposterior dorsal rib fractures and dorsal neural spine fractures in iguanodontians have been associated with bearing the weight of the male during copulation. (Rothschild)

30. Cavernous Bone Made up of various compact bone with centimeters wide internal spaces. Known in extant species of bird bones associated with air sac systems and elephant skull bone. Cavernous bone is present in the ribs and vertebrae in theropods and sauropods, formed during large scale reconstruction. Cavernous bone implies lighten mass and its been suggested to be pneumatic. Using extant phylogenetic bracket approach (EPB) Wendel proposed that sauropod vertebrae are correlates to air sacs in birds.

31. Dental Bone Dinosaurs are similar to basal archosauromorphs and crocodilians in their bones of attachment. Dinosaur teeth are formed in deep grooves of tooth bearing bones, with teeth sockets being alveolar bone Allosaurus, Camarasaurus, amptsaurous and Marshosaurus.

32. Conclusion Dinosaur bone microstructure is well preserved, and has been used to understand the various bone tissue types that existed in dinosaurs. Different parts of the skeleton, bones and crosssections can have multiple bone tissue types present. Several types of compact and cancelluos bone have been identified. The bone tissue types have been used to gain insight on the qualitative rate of formation and how the bones formed. Using EPB approach biological implications of dinosaur bones can be inferred. Ex pneumatic structures in sauropods.

33. Question: There are two types of bone primarily found in the dinosaurs. Pick one type (and its subtypes), and explain the biological implications associated with the microstructure present.