Dinosaur Bone Histology: Understanding Growth Patterns and Metabolism

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Dinosaur Bone Histology Objectives: ● To understand the difference in bone tissue types and their location within bones. ● To learn that different types of animals have different growth patterns that are reflected in their bones. Thermoregulation in Animals Endotherms are animals that generate heat inside their bodies to regulate their temperatures to maintain a stable internal body temperature as outside temperatures vary; whereas ectotherms cannot and must derive their body temperatures by the outside environment and generally cannot remain active in a wide range of temperatures. Metabolism is the process by which cells use energy to do biological work, such as growing new tissues, locomotion, and reproduction. Energy is produced in the form of ATP by breaking down food that is consumed through cellular respiration. In the process of doing biological work, some of the chemical energy in food is converted into heat. The rate at which animals transform chemical energy in food and release heat is the metabolic rate, which is measured in joules, or calories, per second. At similar masses, the metabolic rates of endotherms at rest tend to be 5-20 times greater than those of ectotherms. A higher metabolic rate allows endotherms to be more active, grow faster, and reproduce faster at a range of temperatures; however, they must eat much more often than ectotherms. Thus, mass and metabolic rates can be used to differentiate between ectotherms and endotherms. Bone Size and Mass Bone size generally correlates with the mass of an animal. Bones can be both an indicator of mass and they can tell you something about an animal's metabolism. Similar to trees, bones can have growth rings, in which the number of rings tells you the age of the animal and the width tells you how fast it grows. Scientists can use growth rings to estimate the resting metabolic rate of animals, particularly dinosaurs which are only known from their fossilized remains. The controversial debate of whether dinosaurs were cold-blooded (ectothermic) or warm-blooded (endothermic) is still very much unresolved. Many scientists thought that the study of dinosaur bone tissues, or histology, would provide the answers to the cold-blooded vs warm-blooded debate. However, dinosaur bones turned out to be much more complicated than previously realized. The following lists characteristics of different types of bones as they relate to thermoregulation. Bird and Mammal Bones (warm-blooded / Endotherms):

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 ● Fast growing, collagen fibrils form in a haphazardly manner, fibro-lamellar bone ● Highly vascular, osteons or haversian systems are formed around a blood vessel or the haversian canal ● Determinate growth: bones stop growing at maturity, peripheral rest lines on the outer edge of the bone Reptile Bones (cold-blooded / Ectotherms): ● Slow growing, collagen fibrils form parallel to each other, highly organized lamellar-zonal bone ● Vascular, but blood vessels are rarely found within an osteon ● Continuous and intermittent growth in length and diameter throughout life; dependent on external factors, such as diet, seasonal influences, etc. Bones show growth rings much like trees; reptilian bones can show wide zones of fast growth and narrower regions of slow growth, separated by lines of arrested development (LAGs) Dinosaur Bones ● Commonly fibro-lamellar, highly vascular with osteons

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 ● Some dinosaur bones showed growth rings in the pelvic girdle and humerus; zones were fibro-lamellar (like birds and mammals) while the annuli were similar to modern reptiles; however, other dinosaurs showed no growth rings For more information and practice on bones, click the link below: https://askabiologist.asu.edu/bone- lab#skeleton

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Part I. Anatomy of a Bone and Histology Exercise 1. Using the word list below, label the parts of the long bone. Some words may be used twice. (6 pts, 0.5 pts each). Diaphysis Cancellous (Spongy) Bone Bone Marrow Proximal Epiphysis Endosteum Distal Epiphysis Periosteum Medullary Cavity Articular Cartilage Epiphyseal Growth Plate Compact (Dense) Bone 1. Articular cartilage 5. Hard bone 9. Epiphyseal growth plate 2. Spongy bone 6. Endosteum 10. Proximal epiphysis 3. Spongy bone 7. Bone marrow 11. Diaphysis 4. Medullary cavity 8. Periosteum 12. Distal epiphysis

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Exercise 2. Use the following images (Figure 1A-4D) to fill in the table below. Identify the characteristic structures, if present, for each bone: osteon, osteocyte, trabeculae, Haversian canal, peripheral rest lines, lines of arrested development. Use a n ‘X’ to indicate the presence of that characteristic in each figure. Be aware that some slides contain both compact and cancellous bone. (16 pts, 2 pts each) Cancellous Bone Compact Bone Figure # Trabeculae Present? Peripheral Rest Lines LAGs How many? Haversian Canals Osteon How Many? Osteocyte 1A NA X NA X X 7 X 2B X X X 4 X X 19 NA 3C X NA X 2 X X 15 NA 4D NA X X 10 X X 29 NA 5E NA X X 2 X X 1 X 6F X X NA X X 72 X

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 7G X X NA X X 9 X 8H X X NA X NA X Figure 1A. Long-bone microstructure of Trinisaura santamartaensis .

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 2B. Bone microstructure from Lirainosaurus sp. (sauropod).

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 3C. Histologic structures visible in the tibia of the diplodocoid sauropod Suuwassea emilieae.

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 4D. Bone microstructure from the left tibia of the prosauropod P. engelhardti.

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 5E. Psittacosaurus right radius. 5E

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 6F. Emu pedal digit III, phalanx 1. 6F

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 7G. Ankylosaurid. 7G

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Figure 8H. Nodosaur. 8H

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 QUESTION: Use the thin section below to approximate the age of the turtle? (1 pt). The turtle is about 6 years old.

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 Part II. How Did Dinosaurs Regulate Their Body Temperatures? 1. Mammals and birds are generally endothermic; whereas reptiles and fish are ectotherm. In the table below, identify the body temperature type (endothermic or ectothermic) of the following extant animals. Animal Type of Animal Body Temperature Type? Metabolic Mass (g) Metabolic Rate (joules/s) Chimpanzee Mammal Endothermic 45000 52.32 Alligator Reptile Ectothermic 1287 0.67 Horse Mammal Endothermic 260000 362.9 Raven Bird Endothermic 1203 5.534 Tiger Mammal Endothermic 137900 133.9 Elephant Mammal Endothermic 3672000 2336.0 Gila Monster Reptile Ectothermic 463.9 0.148 Python Reptile Ectothermic 1307 0.13 Lemon Shark Fish Ectothermic 1600 0.959 Patridge Bird Endothermic 475 1.961 Cod Fish Ectothermic 761.1 0.045 Spear-Nosed Bat Mammal Endothermic 84.2 0.559 Raven Bird Endothermic 1203 5.534 Nile Crocodile Reptile Ectothermic 215.3 0.064

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 2. Use Excel to plot the data of metabolic mass (g) and metabolic rate (joules/s) on a graph for each dataset (endotherms, ectotherms). You will need to plot the data on a logarithmic scale for both axes (i.e., a log-log graph). Be sure to label the axes, include a legend, and include a line of best fit for each dataset. Copy and paste your graph in the space below. (4 pts) 3. Look at the general trends on the graph. How do the metabolic rates of endotherms compare with those of ectotherms? (2pts) Ectotherms have a much more drastic increased metabolic rate as metabolic mass increases while Endotherms are mostly all within a similar range. 0.01 0.1 1 10 100 1000 10000 1 10 100 1000 10000 1000001000000 10000000 Matabolic Mass Metabolic Rate Endo metabolic rate Ecto metabolic rate Linear (Endo metabolic rate) Linear (Ecto metabolic rate)

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 4. Make a prediction of whether you think dinosaurs were more like endotherms or ectotherms. Explain. How do you think dinosaurs will compare with the birds denoted with an “*”? (2pts) I think that dinosaurs are more similar to ectotherms because the data points follow similar trends. I think they will be even more similar because they share more common ancestry. 5. Use the same graph and plot the following data for each dinosaur. Be sure to include a line of best fit for the dinosaur data points. Animal Type of Animal Metabolic Mass (g) Metabolic Rate (joules/s) Allosaurus Dinosaur 1862 205.85 Apatosaurus Dinosaur 19170 2999.04 Coelophysis Dinosaur 33 7.405 Troodon Dinosaur 52 10.956 Tyrannosaurus Dinosaur 5654 853.38 6. Copy and paste your updated graph with dinosaurs in the space below. (3 pts)

GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 7. Does the relationship between mass and metabolic rate in dinosaurs follow a pattern more similar to ectotherms or endotherms? From an evolutionary perspective, how could mesothermy have been an advantage for dinosaurs? (2pts) It follows the same pattern as ectotherms. Mesothermy is a mix between warm and cold blooded. This could be useful because during times of good climate, dinosaurs wouldn ’ t have to waste energy like endotherms. However when the weather is bad, dinosaurs would be able to self-regulate and survive. 8. Grady et al. (2014) concluded that dinosaurs were mesotherms. Why do you think these scientists describe dinosaurs this way, and do you agree with their conclusion? Explain. (2pts) I think they are described this way because they follow the same data patterns as ectotherms but they ’ re ancestors are endotherms. I agree with this conclusion because it makes sense that dinosaurs would be able to do this. 0.001 0.01 0.1 1 10 100 1000 10000 1 10 100 1000 10000 1000001000000 10000000 Matabolic Mass Metabolic Rate Endo metabolic rate Ecto metabolic rate Dino metabolic rate Linear (Endo metabolic rate) Linear (Ecto metabolic rate) Linear (Dino metabolic rate)

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GEOL 207: Dinosaur World Name: __Matthew Reckleben__________ Lab Section: 500 501 502 503 504 505 9. Discuss any biases or issues with data used to create the dinosaur trend line. Hint: which clade of dinosaurs are more closely related to modern birds? (2pts) All the dinosaurs in this experiment are in the saurischian clade, which is the same clade that is more closely related to birds. This means they are more likely to be warm blooded like birds are. We can see that our trend line for dinosaurs is very similar to our trend line for endotherms, even though it should be in the middle because we know dinosaurs are mesotherms. 10. How might your graph differ with the inclusion of other dinosaur taxa? Be specific with the dinosaur clades that you would include. (2pts) If we included other dinosaur taxa, I would have included other ornithischian dinosaurs. I would have included triceratops, iguanadon, heterodontosaurus, and stegosaurus. I hypothesize that including these dinosaurs would yield more data points in the top right section of our graph, as they are less likely to be warm blooded like birds than the saurischian dinosaurs.

Online Dinosaur Bone Histology Handout F21

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