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Mammalogy
The Evolution of Mammals
| Term | Definition |
|---|---|
| Plecosauria | - Early Permian. - Varied diet and activity. - Large Dorsal Sail. - 3 meters long. |
| Ancestral Characteristics of: Plecosauria | - Weakly heterodont. - Angular/articular in mandible. - Single occipital condyle. - No secondary palate. |
| Early Therapsida | - Middle Permian. - Active and diverse. - Some dominant herbivores for 60 million years. - Extinct after Permian-Triassic Event. |
| Derived Characteristics of: Early Therapsida | - Enlarged temporal opening. - Partial secondary palate. - Major skull and jaw changes. |
| Advanced Therapsida | - Includes Cynodonts. - Triassic to mid-Jurassic. - Diverse herbivores and carnivores. - Conflict over rather one or more than one line gave rise to modern mammals. |
| Mammalian Characteristics of: Advanced Therapsida | - Double occipital condyle. - Complete secondary palate. - Expansion of temporal opening and brain case. - Strongly heterodont dentition. |
| Early Mammals | - 250 million years ago. - Overlapped with Cyodonts and dinosaurs. - Small and nocturnal. |
| Early Prototherians Include... | - Morganucodontids. - Triconodonts. - Docodonta. - Multituberculata. |
| Morganucodontids | - Early Prototherian - Small (10 cm). - Good hearing. - Probably nocturnal. - Expanded dentary bone with dentary-squamosal articulation. - Mammalian posture. |
| Triconodonts Include... | - Jeholodens. - Repenomamus giganticus. |
| Jeholodens | - Triconodont - Derived pectoral girdle. - Ancestral pelvic girdle. |
| Repenomamus giganticus | - Triconodont - Largest mammal of Cretaceous period - 1 m long and 12-14 Kg - Fed on young dinosaurs |
| Docodonta | - Early Prototherian - Late Jurassic period. - Complex teeth, omnivores. - Primitive jaw articulation. |
| Multituberculata | - Early Prototherian. - Diverse and persistent (lasted 120 million years starting in Jurassic). - Mouse to marmot size. - Overlap with modern mammals. - Unique dentition with chisel like incisors and 8 grinding molars. - Exploitation of niches. |
| Early Therians Include... | - Symmetrodonta (Insectivores). - Eupantotheria. - Tribosphenic molars, basic for later mammals, for shearing and grinding |