BI2CV1 Comparative Vertebrate Biology Lecture Notes PDF

BI2CV1 Part 2 – Semester 1 2024-2025 Comparative Vertebrate Biology Lecture 3 – Skeletons (Part 1): Terminology; axial and appendicular skeleton Dr Brian John Pickles [email protected] 1 Copyright University...

BI2CV1 Part 2 – Semester 1 2024-2025 Comparative Vertebrate Biology Lecture 3 – Skeletons (Part 1): Terminology; axial and appendicular skeleton Dr Brian John Pickles [email protected] 1 Copyright University of Reading Overview To appreciate and confidently compare vertebrate anatomy you need to be able to understand and describe the skeleton Today’s lectures are going to focus on anatomical terminology and the different parts of the skeleton Part 1: The Axial and Appendicular skeleton Part 2: The Cranial skeleton 2 Learning Outcomes We have two lectures on skeletons and the plan is to cover the following: Part 1 LO1: Basic anatomical terminology LO2: Head, neck, and trunk - the axial skeleton LO3: Limbs and girdles - the appendicular skeleton Part 2 LO4: Skulls – the cranial skeleton (Part 2) LO5: Comparisons between vertebrates 3  Lepidosauria Squamata Rhynchocephalia Lepidosauromorpha Plesiosauria Icthyosauria Saurischia Aves Diapsida Dinosauria Other saurischians Sauropsids Avemetatarsalia Ornithschia Archosauria Pterosauria Reptilia Crocodylia Crurotarsi Other crurotarsians Amniota Testudines Non-diapsid reptiles Synapsida Mammalia Mammals Tetrapoda Other synapsids Lepospondyli Caudata Lissamphibia Anura Amphibians Tetrapodomorpha Gymnophiona Dissophoroidea Other Temnospondyls Sarcopterygii Dipnoi Lungfish Mesozoic Cenozoic Actinistia Coelocanths Paleozoic Mesozoic Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Tertiary Quaternary 4 400 Mya 350 Mya 300 Mya 250 Mya 200 Mya 150 Mya 100 Mya 50 Mya Present Anatomical terminology There are several key terms that you will need to become familiar with to get the most out of anatomy: The Frontal plane (or dorsal plane) Dorsal – upper side, or back Ventral – underside, towards the belly The Transverse plane Anterior or Cranial – front, towards the head Posterior or Caudal – rear, towards the tail Dorsal Posterior Anterior 5 Ventral Anatomical terminology There are several key terms that you will need to become familiar with to get the most out of anatomy: The Sagittal plane Medial – towards the midline Medial Lateral – away from the midline Lateral Medial 6 Lateral Anatomical terminology There are several key terms that you will need to become familiar with to get the most out of anatomy: Proximal – nearer to the centre of the body or attachment point Distal – away from the centre of the body or attachment point 7 Skeletons Due to common ancestry skeletons share certain features in common This allows us to compare them more easily We divide them up into specific areas: Axial skeleton (head, neck, trunk) – This lecture Appendicular skeleton (girdles, limbs) – This lecture Cranial skeleton (Skull) – Next lecture 8 Axial vs Appendicular Axial skeleton (yellow) Skull Vertebrae (neck, trunk, tail) Ribs Appendicular skeleton (red & blue) Pectoral girdle (shoulders) Forelimbs Pelvic girdle (hips and sacrum) Hindlimbs Juvenile saltwater crocodiles Crocodylus porosus 9 Axial skeleton The axial skeleton consists of the head, neck, and trunk Skull, vertebral column, rib cage We will come back to the bones of the skull in the next lecture Vertebral column aka the spine Several different sections Shapes and functions differ Different types of vertebrae in different taxonomic groups Ribs Rod-like bones lateral to vertebrae Provide structure for body wall and attachment points for muscles 10  Human vertebrae The Vertebral Column 11 The Spine - vertebrae Names relate to specific positions along the spine: Cervical (neck) Thoracic / dorsal (back, with ribs) Lumbar (lower back; mammals) Sacral (pelvic region) Caudal (tail) 12  The Spine - vertebrae Main differences between tetrapods Diapsida Amphibia 13 Figure from Jones et al. 2022: https://www.science.org/doi/epdf/10.1126/science.aar3126  Vertebrae – key features Vertebrae articulate with each other but also with the skull, ribs, and hips Wide range of morphologies but some conserved features Vertebral foramen = neural canal Vertebral body = centrum Vertebral arch = pedicle and lamina Transverse processes = diapohyses (muscle / rib attachment) Superior articular process = prezygapophysis Inferior articular process = postzygapophysis Spinous process = neural spine Capitular process 14  Example of Snake vertebrae Zygosphene and Zygantrum Accessory articulation in some lepidosaurs (lizards & snakes) Additional joint that provides stability for the vertebral column 15  Vertebral Centra - shapes Different shapes articulate in different ways Shapes generally correspond to taxonomic groups Amphicoelous: fish Procoelous: reptiles Opisthocoelous: sturgeon and salamanders Acoelous: birds, mammals Heterocoelous: bird necks 16  Ribs and rib cage Ribs are essentially rods that attach laterally to the vertebrae Tuberculum Provide structure that supports the body wall Attachment points for muscles Can be found in neck, body, and/or tail depending on the taxon Capitulum In tetrapods the tuberculum articulates with the diapophysis (transverse process; A) the capitulum articulates with the parapophysis (capitular process; B) 17  Ribs and rib cage Rib cage results from the ribs encircling the body Protects organs Support for body Muscle attachment Mouse Gecko Snake 18 Example: Sauropoda Cervical ribs Dorsal ribs 19  Gastralia Extension of the rib cage that support the abdominal wall Found in: many early archosaurs crocodilians the tuatara some lepidosaurs Dinosauria, but not Aves 20  Special case - Testudines Testudines are unique among vertebrates Vertebrae and ribs are fused into their carapace Vertebrae fuse with neurals Ribs fuse with costals 21  Axial skeleton evolution Analysis of Tiktaalik and other early tetrapods shows that: i. novel rib types arose prior to major changes in trunk vertebrae ii. links between pelvic fins and the Purple = ribs axial column came before the Blue = pelvic girdle origin of limbs See Stewart et al. 2024 22 https://doi.org/10.1073/pnas.2316106121 Axial vs Appendicular Axial skeleton (yellow) Skull Vertebrae (neck, trunk, tail) Ribs Appendicular skeleton (red & blue) Pectoral girdle (shoulders) Forelimbs Pelvic girdle (hips and sacrum) Hindlimbs Juvenile saltwater crocodiles Crocodylus porosus 23 Appendicular skeleton The appendicular skeleton is essentially all the bones not in the axial skeleton the bones that append to the axial skeleton Manus Arm Shoulder girdle Leg Juvenile saltwater crocodiles Pelvic girdle Crocodylus porosus Pes 24 Pectoral girdle In fish: the pectoral girdle is attached to the skull In tetrapods the pectoral girdle is attached to the axial skeleton with muscles and ligaments 25 Pectoral girdle in humans… 26 …and other taxa Current view of shoulder girdle evolution in vertebrates. Key elements: 1. cleithra 2. scapulocoracoid (fish only) 3. clavicle 4. interclavical 5. coracoid 6. scapula 27 Ponomartsev et al. 2017 Bio. Comm. 62(1): 26–37. doi: 10.21638/11701/spbu03.2017.104 Pelvic girdle In fish the pelvic girdle is not attached to the axial skeleton In tetrapods the pelvic girdle articulates with the vertebrae Formed of: ilium, ischium, and pubis acetabulum (concavity where femur-pelvis form hip joint) acetabulum dorsal lateral 28 Gecko Girdles in Testudines Testudines (turtles and tortoises), and Manus many of their precursors in the Arm Testudinata, are the only vertebrates that have their limb girdles contained within Shoulder their rib cage girdle This has functional consequences Movement Breathing Etc. Leg Pelvic girdle Pes 29 Limbs Limbs in tetrapods have evolved from the fins of our fish ancestors We can trace the evolution of specific bones 30 Limbs This sequence shows the likely transition from fins to forelimbs Note individual bones 31 Forelimbs Humerus Forelimbs Humerus (upper arm bone) Radius and Ulna (forearm bones) Radius Ulna Carpus (wrist bones) Manus (bones of the hand) Manus In Anurans the radius and ulna fuse Toad Radioulna Radioulna 32 Forelimbs Manus (the hand) wrist (carpus; carpal bones) palm bones (metacarpals) digits (phalanges) claws (unguals) Whale Unguals 33 Hindlimbs Sauropod Hindlimbs Canine Femur (upper leg bone) Tibia and Fibula (central leg bones) Tarsus (ankle bones) Pes (bones of the foot) Femur Fibula Tibia Tarsals Metatarsals Phalanges Unguals 34  Aves Hindlimbs Hindlimbs Femur (upper leg bone) Tibia and Fibula (central leg bones) Tarsus (ankle bones) Pes (bones of the foot) In Aves the tibia and tarsus fuse Tibiotarsus Anuran In Anurans the tibia and fibula fuse Tibiofibula 35 Hindlimbs Mammal Squamate Aves Pes (the foot) ankle (tarsus; tarsal bones) foot bones (metatarsals) digits (phalanges) Ornithiscian claws (unguals) Mammal (human) 36 Styracosaurus albertensis Humerus Radius Femur Metacarpals Tibia Fibula Metatarsals Phalanges Ulna Phalanges 37 Manus Pes Digit numbering systems Digits are identified using roman numerals I-V moving medially to laterally So ‘thumb’ is I and ‘pinkie’ is V Ancestor of living tetrapods had 5 digits Many lineages have lost some avian pes typically has digits I-IV avian manus typically has digits I-III* Digit formula: phalanges are numbered Medially to laterally Human manus: 2-3-3-3-3 Tyrannosaurus rex manus: 2-3-0-x-x 38 *Sometimes considered to be digits II-IV  Digit numbering systems Example of how digits have been retained or lost in modern Archosaurs Crocodilian manus = 5 digits Avian manus = 1-3 digits Crocodilian pes = 4 digits Avian pes = 2-4 digits de Bakker, M., Fowler, D., Oude, K. et al. Digit loss in archosaur evolution and the interplay between selection and constraints. Nature 500, 445–448 (2013). 39 https://doi.org/10.1038/nature12336  Limbs and locomotion Fusion of bones and changes in posture correspond to how animals move Here we can see differences between extant mammals: Fusion of leg bones Loss/fusion of digits Shift of stance onto toes and digits Ungulates – claw becomes hoof Whole Toes and Tips of foot digits toes only 40  Limbs and locomotion Fusion of bones and changes in posture correspond to how animals move We can use the same principles to examine how extinct taxa might have walked Were sauropods: Digitigrade Mid-digitigrade Subunguligrade Compare with modern elephants See Jannell et al. 2022 DOI: 10.1126/sciadv.abm8280 41 Learning Outcomes - Revisited LO1: Basic anatomical terminology Frontal, transverse, and sagittal planes; proximal vs. distal LO2: Head, neck, and trunk - the axial skeleton Vertebrae, processes, ribs, gastralia LO3: Limbs and girdles - the appendicular skeleton Paired forelimbs and hindlimbs; pectoral girdle; pelvic girdle; digit numbering 42 Next: Lecture 4 - Skeletons: Part 2 – Cranial bones 43