Modified office hours today: 3-4 Ceratopsia: Shared, Derived - - PowerPoint PPT Presentation

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Modified office hours today: 3-4 Ceratopsia: Shared, Derived - - PowerPoint PPT Presentation

Dec 22, 2023 26 likes •521 views

Modified office hours today: 3-4 Ceratopsia: Shared, Derived Characteristics Ornamentation on posterior margin of skull Typically a frill; modified parietal bone Skull with narrow & deep beak-like snout Flared cheeks (results in

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Modified

  • ffice hours today:

3-4

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Ceratopsia: Shared, Derived Characteristics

Ornamentation on posterior margin of skull Typically a frill; modified parietal bone Skull with narrow & deep beak-like snout Flared cheeks (results in triangular shaped skull when viewed from the top) Rostral Bone: UNIQUE! New bone on tip of upper jaw Covered by a horny beak

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Rostral bone

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Ceratopsia

Psittacosaurus: ‘Parrot Lizard’

Short, almost round dorsal profile Very unique!

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Psittacosaurus: ‘Parrot Lizard’

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Psittacosaurus: ‘Parrot Lizard’

Shared, derived Characteristics Small naris; positioned higher on skull Reduction of 2 outer digits Forelimb relatively long: Bipedality Aid for foraging?

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Psittacosaurus SKIN

Preserved skin from a China specimen Most of the body covered in large, irregular scales Hollow tubular bristles arranged down the tail No evidence that these structures are related to Saurischian feathers but jury is still out Possibly convergently evolved feather-like structures Communication? Display? Very cool.

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Psittacosaurus Social Lives Amazing nests Suggests some degree of maternal care

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How embarrassing...

Juvenile Psittacosaurus found in the stomach

  • f an early Cretaceous mammal:

Repenomamus robustus

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Archaeoceratops Basal Neoceratopsian Known from North-Central China; found in Early Cretaceous rocks Hallmarks of more derived Neoceratopsians: Emphasized boney frill Larger head:body size ratio 3 fused vertebrae to support large head Upwardly hooked lower beak All Neoceratopsians (except most basal) => quadrupedal

Archaeoceratops Ceratopsidae Neoceratopsia Psittacosaurus

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Psittacosaurus Archaeoceratopsia

Modern Mongolia-region Modern China Early Cretaceous

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Protoceratopsians

Ceratopsia Psittacosaurus Asia North America

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First eastward migration early-mid Cretaceous

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Bagaceratops Protoceratops Leptoceratops Montanoceratops Early => Late Cretaceous Primitive in FORM vs. Primitive in TIME

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Basal Neoceratopsia

Chaoyangsaurus Liaoceratops Archaeoceratops Leptoceratops Bagaceratops Protoceratops More derived forms have: Larger parietal frills Large bilateral fenestrae (openings) Broad nasal lump over nares

Archaeoceratops Protoceratops

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Roy Chapman Andrews

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Roy Chapman Andrews: Gobi Expedition 1923-1925

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Roy Chapman Andrews: Gobi Expedition 1923-1925

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Earliest Ceratopsian dinos: Primarily Asia Early Neoceratopsian dinos: Asia and North America Ceratopsidae dinos: North America only Derived Late Cretaceous

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Late Cretaceous

Western Interior Seaway

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Protoceratopsians Psittacosaurus

Ceratopsidae is divided into 2 major subgroups: Centrosaurs Chasmosaurs ALL NORTH AMERICAN LATE CRETACEOUS

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Shared, derived traits of Ceratopsidae

Enormous skulls (up to 8.5 ft among Torosaurus) Western North America (Alaska => New Mexico) Latest Cretaceous Large frills Orbital or nasal horns/protuberances Large nasal openings Complex dental battery

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vs.

probably semi-erect sprawling erect

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Diet! (Ceratopsidae)

Complex dental battery Double-rooted teeth: structural support Adjacent teeth are locked together to maximize cutting edge As teeth are worn, they are replaced by new teeth below ~ Never run out of teeth Top teeth are self-sharped by cutting action
 Large hyoid: long tongue Musculature! Large chewing muscles attached from a large coronoid process on the lower jaw up through the upper temporal opening and onto the frill

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Ceratopsidae dental battery... Analogous to the Hadrosaur dental battery Not related- convergent evolution! Triceratops teeth Hadrosaur teeth

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Diet! (Ceratopsidae)

Large coronoid process for chewing muscle attachment

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Parietal Frill Squamosal Frill

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Protoceratopsians Psittacosaurus

Ceratopsidae is divided into 2 major subgroups: Centrosaurs Chasmosaurs ALL NORTH AMERICAN LATE CRETACEOUS

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Centrosaurs (short-frilled)

Centrosaurus Achelousaurus Einiosaurus Styracosaurus Avaceratops Long nasal horns Hooks and processes on the parietal frill (sometimes SPIKES!) Some (Pachyrhinosaurus) had pitted/grooved pads Pachyrhinosaurus

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Centrosaurs

Avaceratops Styracosaurus Centrosaurus 6 m Achelousaurus

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Centrosaurs

Avaceratops Einiosaurus Centrosaurus Styrachosaurus Achelosaurus Pachyrhinosaurus

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Pachyrhinosaurus Boney pads Pitted and grooved surface Potentially an attachment site for a keratinous horn?

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Einiosaurus

Some nasal horns had alternate uses

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Einiosaurus

Some nasal horns had alternate uses

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Centrosaurs: Bone Beds

Monotypic: Single species Herding behavior or mass grouping Did they nest? Less well known... But: Juveniles, subadults, adults aggregated in bonebeds Implies family units, herds

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Protoceratopsians Psittacosaurus

Ceratopsidae is divided into 2 major subgroups: Centrosaurs Chasmosaurs ALL NORTH AMERICAN LATE CRETACEOUS

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Chasmosaurus Kind of a badass

Chasmosaurs (long-frilled)

Long orbital horns Short nasal horns Complex sinus cavities in skull Not found in Bone Beds

Triceratops Torosaurus 8 meters! 2.6 m (8.5 ft long skull) Pentaceratops Arrhinoceratops

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Anchiceratops

Chasmosaurs

Chasmosaurus Chasmosaurus Chasmosaurus Arrhinoceratops Torosaurus Triceratops Triceratops Pentaceratops

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Triceratops horn growth stages Chasmosaurs: babies all look the same

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Sexual dimorphism? Late frill development

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Horns and Frills: Defense or competition?

All Ceratopsians have: long horns, short horns or thickened pads of bone near nares or orbitals Frill: Very thin- not adequate defense; indications of high vasculature This suggests head to head sparing among males and display Display: to females, to other males, and to distinguish among species BUT: also defense... similar to antelope horns (remember the Oryx)

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Where you predict to find damage if they were horn-locking Where you find damage

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