Lab6_Excavation Stage II
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Texas A&M University *
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Course
207
Subject
Geology
Date
Apr 3, 2024
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5
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Dinosaur Excavation Stage II Part I: Excavation Stage II – Caudal Region Below is “site map” image of the excavation site(s). These images, and others you will need to complete this assignment, are available at: https://sites.google.com/tamu.edu/geol-207-dinosaur-world-
ex2/home
. An arrow is labeled in the top right corner of your image indicating the direction of North. On your site map image, each bone has been numerically labeled. 1)
Identify and Catalog the Bones: Use Table 2 below to catalog the bones recovered during the excavation. For each numbered bone, you should identify the type of bone and the region of the body the bone is from
(in this lab, all bones are from the caudal region). Under notes, provide any features present that are important sharded derived characters that could help you in your identification. You should also provide an approximate measurement for each bone marked with a * using the scale bars on the zoom-in photos available at
: https://sites.google.com/tamu.edu/geol-
207-dinosaur-world-ex2/home Table 2. Bone catalog for Excavation Stage II. (10 pts) Bone Number Bone Identification Skeletal Region Measurements Other Notes Length (cm) Width (cm) 22* Caudal Vertebrae caudal
40 20 23 Caudal Vertebrae caudal
-- -- 24 Caudal Vertebrae caudal
-- -- 25 Caudal Vertebrae caudal
-- -- 26 Caudal Vertebrae caudal
-- -- 27 Caudal Vertebrae caudal
-- -- 28 Caudal Vertebrae caudal
-- -- 29 Caudal Vertebrae caudal
-- -- 30 Caudal Vertebrae caudal
-- -- 31 Caudal Vertebrae caudal
-- -- 32 Caudal Vertebrae caudal
-- -- 33 Caudal Vertebrae caudal
-- -- 34* Caudal Vertebrae caudal
20 23
35 Caudal Vertebrae caudal
-- -- 36 Caudal Vertebrae caudal
-- -- 37 Caudal Vertebrae
caudal
-- -- 38 Caudal Vertebrae caudal
-- -- 39 Caudal Vertebrae caudal
-- -- 40 Caudal Vertebrae caudal
-- -- 41* Caudal Vertebrae caudal
15 22 42 Caudal Vertebrae caudal
-- -- 43 Caudal Vertebrae caudal
-- -- 44 Caudal Vertebrae caudal
-- -- 45 Caudal Vertebrae caudal
-- -- 46 Caudal Vertebrae caudal
-- -- 47* Caudal Vertebrae caudal
7 19 48* Caudal Vertebrae caudal
100 18 End of the Tail 49 Chevron caudal
-- -- 50* Chevron caudal
4 30 51 Chevron caudal
-- -- 52 Chevron caudal
-- -- 53 Chevron caudal
-- -- 54 Chevron caudal
-- -- 55 Chevron caudal
-- -- 56 Chevron caudal
-- -- 57 Chevron caudal
-- -- 58 Chevron caudal
-- -- 59 Chevron caudal
-- -- 60* Chevron caudal
61 Chevron caudal
-- -- 62 Chevron caudal
-- -- 63 Chevron caudal
-- -- 63 Chevron caudal
-- -- 65 Chevron caudal
-- -- 66 Chevron caudal
-- -- 67 Chevron caudal
-- -- 68 Chevron caudal
-- -- 69 Chevron caudal
-- -- 70 Chevron caudal
-- -- 71 Chevron caudal
-- -- 72 Chevron caudal
-- -- 73 Chevron caudal
-- -- 74 Chevron caudal
-- -- 75* Chevron caudal
8 8
2)
Interpret the Skeleton (5 pts) a)
What is the approximate total length of the tail? Be sure to use the scale bars in the images determine the length. (1 pt)
The approximate length of the tail based upon the scale bars in the images is likely 3.5 meters or 350 cm. b)
Describe how the size of the caudal vertebrae changes from the proximal to the distal end of the skeletal remains? (1 pt)
As you move from the proximal to the distal end, the caudal vertebrae decrease. c)
Is the tail flexible or not? State you claim, provide your evidence, and explain your reasoning. (2pts)
The tail is not flexible. An examination of the remaining bones shows that the tail lacks the typical features associated with flexibility, such as joints or segments that allow for movement. Therefore, the claim that the tail is not flexible is supported. d)
Describe how the size and shape of the chevrons from anterior to posterior of the organism? (1 pt)
The size of the chevrons increases, while the shape changes from a more so triangular shape to a long cylindrical shape as you move from the anterior to the posterior of the organism. 3)
Evaluate your evidence to reach a preliminary identification (10pts)
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a)
Given your observations of the caudal region, which major group(s) could this specimen belong to? State your claim (the clades), list your evidence, and explain your reasoning. (5 pts) Given my observation of the caudal region. The major group this specimen could belong to is the Clade Titanosaur. The combination of the long, whiplike tail with elongated and articulated vertebrae, along with other observed features, strongly indicates similarities with that of the Titanosaur clade. Titanosaurs were a group of sauropod dinosaurs known for their large size and distinctive anatomical features, including their long tails. The vertebrae in the caudal region are elongated and cylindrical, with some variation in size which is a characteristic of the Titanosaur. The Chevron bones of the observed caudal region are slender bones that articulate with the caudal vertebrae which is also a characteristic of the Titanosaur. Overall, based on the observed characteristics of the caudal region, the specimen is most likely remember of the Titanosaur clade. b)
Are there any dinosaur groups that your evidence can rule out? State you claim (“This could not be the Clade X…”), list your evidence, and explain your reasoning. (5 pts) The evidence suggests that the fossil skeleton in question is unlikely to belong to either the Clade Ankylosaur or the Clade Spinosaur. This could not belong to the Clade Ankylosaur since there is a presence of a club-like feature on the anterior part of the caudal region is characteristic of the Ankylosaur clade. However, upon examination of the fossil skeleton, no such club-like feature is observed. This absence of a distinctive club structures rules out the possibility of this skeleton belonging to the Ankylosaur clade. This could not belong to the Clade Spinosaur since they typically exhibit long and mostly consistent in size chevrons. However, the fossil skeleton under examination does not display such features. Instead, the chevrons, or the bones along the underside of the tail, exhibit variations in size or morphology inconsistent with the typical characteristics of Spinosaurs.
4)
Interpret the Paleoecology and Environment (5 pts) To place a fossil skeleton in the a paleoecological and environmental context, we often look for the nearby remains of other organisms as well as biogenic sedimentary structures are called trace fossils
. Trace fossils, or ichnofossils
, are traces of living organisms (
such as burrows, trackways, root marks, etc
.) that have been preserved in the substrate and provide evidence for the organism’s behaviors. Certain trace fossils can only be preserved in a specific type of depositional environment, thus they can also be used in paleoenvironmental interpretation. There are two sets of trace fossils were preserved near the caudal region of this skeleton.
a.
Examine Assemblage A on the dorsal side of the caudal region. What type of fossils are presented in this assemblage? (1 pt)
The type of fossils that are presented in this assemblage is that they seem to contain other bone fossils and some rock deposits. They are most likely trace fossils. b.
Do you think the fossils in Assemblage A are part of the same individual as the main skeleton? Make your claim, describe your evidence, and explain your reasoning. (2 pts)
I think that the fossils in Assemblage A are most likely not from the same individual. This reason I think this is because it is very unlikely that the caudal vertebrae could be connected to through some sort of calcified tendon that held spikes or a fan-like appearance. c.
The small rounded stones in Assemblage A are gastroliths. What is the function of gastroliths to an organism? Which groups of dinosaurs would you expect to have gastroliths? (1 pt)
A gastrolith is a “stomach” stone or in other words a stone that is swallowed to aid in the digestion of the organism’s food. The group of dinosaurs I would expect to have gastroliths would be herbivorous dinosaurs to help them digest the plants they are eating. d.
Assemblage B near the distal end of the caudal region contains coprolites. What does the preservation of coprolites imply about the environment in which these fossils were preserved? (1 pt)
The preservation of coprolites in Assemblage B near the distal end of the caudal region implies that the environment in which these fossils were preserved likely had conditions conducive to the formation and preservation of fecal matter. Coprolites are fossilized excrement, indicating the presence of organisms capable of defecting in the area.