Aptian

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian, all part of the Lower/Early Cretaceous.^[1]

The Aptian partly overlaps the upper part of the regionally used (in Western Europe) stage Urgonian.

The Selli Event, also known as OAE1a, was one of two oceanic Anoxic events in the Cretaceous period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years.^[2]^[3] The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma.^[4]

Stratigraphic definitions

The Aptian was named after the small city of Apt in the Provence region of France, which is also known for its crystallized fruits. The original type locality is in the vicinity of Apt. The Aptian was introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1840.

The base of the Aptian stage is laid at magnetic anomaly M0r. A global reference profile for the base (a GSSP) had in 2009 not yet been appointed. The top of the Aptian (the base of the Albian) is at the first appearance of coccolithophore species Praediscosphaera columnata in the stratigraphic record.

Subdivision

In the Tethys domain, the Aptian contains eight ammonite biozones:

zone of Hypacanthoplites jacobi
zone of Nolaniceras nolani
zone of Parahoplites melchioris
zone of Epicheloniceras subnodosocostatum
zone of Duffrenoyia furcata
zone of Deshayesites deshayesi
zone of Deshayesites weissi
zone of Deshayesites oglanlensis

Sometimes the Aptian is subdivided in three substages or subages: Bedoulian (early or lower), Gargasian (middle) and Clansayesian (late or upper). In modern formal chronostratigraphy the Aptian is divided into Lower and Upper sub-stages. The Lower Aptian is equivalent to the Bedoulian, and it includes the oglanensis to furcata Tethyan ammonite zones. The Upper Aptian is equivalent to the Gargasian and Clansayesian, it includes the subnodosocostatum to jacobi Tethyan ammonite zones (Gradstein et al. 2004).

Lithostratigraphic units

Examples of rock units formed during the Aptian are: Antlers Formation, Cedar Mountain Formation, Cloverly Formation, Elrhaz Formation, Jiufotang Formation, Little Atherfield, Mazong Shan, Potomac Formation, Santana Formation, Twin Mountains Formation, Xinminbao Group and Yixian Formation.

Palaeontology

Amphibia

Amphibians of the Aptian
Taxa	Presence	Location	Description	Images
†Koolasuchus †Koolasuchus cleelandi		Wonthaggi Formation, Victoria, Australia	A large brachyopoid stereospondyl and the youngest known temnospondyl.	Koolasuchus Liaobatrachus
†Liaobatrachus †Liaobatrachus zhaoi †Liaobatrachus beipiaoensis		Yixian Formation, Liaoning Province, China.	Α genus of prehistoric spadefoot toads and the oldest modern frog known to date. Later discoveries were named Callobatrachus sanyanensis and Mesophryne beipiaoensis until both were classified as synonymous with Liaobatrachus.

†Ankylosaurs

†Ankylosauria of the Aptian
Taxa	Presence	Location	Description	Images
†Cedarpelta †Cedarpelta bilbeyhallorum		Cedar Mountain Formation, Utah, USA		Gobisaurus Minmi Sauropelta
†Gobisaurus †Gobisaurus domoculus		Ulansuhai Formation, Inner Mongolia, China
†Liaoningosaurus †Liaoningosaurus paradoxus		Yixian Formation, Liaoning, China	Nodosaurid with ventral armor plating
†Minmi †Minmi paravertebra		Bungil Formation, Queensland, Australia	Small (1 metre (3 feet)) primitive ankylosaur
†Sauropelta †Sauropelta edwardsorum	Aptian to Albian	Cloverly Formation, Wyoming, Montana, Utah, USA	A medium-sized nodosaurid, measuring about 5 metres (16 feet) long, Sauropelta had a distinctively long tail which made up about half of its body length. Its neck and back were protected by an extensive bony body armor including characteristically large spines
†Shamosaurus †Shamosaurus scutatus		Mongolia	Ankylosaurid

Birds (avian theropods)

†Ceratopsians

†Ceratopsia of the Aptian
Taxa	Presence	Location	Description	Images
†Archaeoceratops †Archaeoceratops oshimai		Mazong Shan, Gansu, China	A basal neoceratopsian, appears to have been bipedal and quite small (about 1 metre (3 feet) long) with a comparatively large head. Unlike many later ceratopsians it doesn't have any horns and has only a small bony frill projecting from the back of its head.	Archaeoceratops Auroraceratops Psittacosaurus meileyingensis Psittacosaurus mongoliensis
†Auroraceratops †Auroraceratops rugosus		Xinminbao Group, Gansu, China, South Korea	Basal neoceratopsian
†Psittacosaurus †Psittacosaurus meileyingensis †Psittacosaurus mongoliensis		China, Mongolia, Russia	Psittacosaurid Ceratopsian
†Serendipaceratops †Serendipaceratops arthurcclarkei		Victoria, Australia	2-metre (7-foot) long early ceratopsian

†Choristoderans

†Choristoderans of the Aptian
Taxa	Presence	Description	Images
†Hyphalosaurus †Hyphalosaurus lingyuanensis †Hyphalosaurus baitaigouensis		Yixian Formation, Liaoning Province, China	Hyphalosaurus Monjurosuchus
†Khurendukhosaurus †Khurendukhosaurus orlovi †Khurendukhosaurus bajkalensis		Mongolia and Russia
†Monjurosuchus †Monjurosuchus splendens		China and Japan
†Philydrosaurus †Philydrosaurus proseilus		Jiufotang Formation, China
†Tchoiria †Tchoiria namsari †Tchoiria klauseni		Hühteeg Formation, Hüren Dukh, central Mongolia

Crocodylomorpha

Crocodylomorphs of the Albian
Taxa	Presence	Location	Description	Images
Anatosuchus	Aptian - Albian	Tegama Group, Niger	A small notosuchian under 1 metre (3.3 ft) long with a duck-like snout.	Anatosuchus
Chimaerasuchus	Aptian - Albian	Wulong Formation, China	The first notosuchian found with heterodont teeth, thought to be a herbivore
Stolokrosuchus		Niger	Initially described as related to Peirosauridae, more recent works usually find Stolokrosuchus to be one of the basalmost neosuchians.

Fish

Mammalia

Mammals of the Hauterivian
Taxa	Presence	Location	Description	Images
Eobaatar	several species from Hauterivian to Albian	Spain, Mongolia		Jeholodens Repenomamus Yanoconodon
Jeholodens		Yixian Formation, Liaoning, China	A long-tailed, nocturnal tetrapod (with prehensile fingers and toes) which hunted insects, its food, during the night
Repenomamus		Yixian Formation, Liaoning, China	The largest mammal known from the Cretaceous period of the Mesozoic, and the one for which there is the best evidence that it fed on dinosaurs.
Sinobaatar		Yixian Formation, Liaoning, China
Teinolophos		Flat Rocks, Victoria, Australia	The earliest known monotreme.
Yanoconodon		Yixian Formation, Hebei, China	A small mammal, barely 13 centimetres (5 inches) long. It was lightly built and fed on insects, worms and other invertebrates, probably hunting at night. Like most early mammals, Yanoconodon had short, sprawling legs and claws that were most likely used for burrowing underground or digging
Zhangheotherium		Yixian Formation, Liaoning, China

†Ornithopods

†Ornithopoda of the Aptian
Taxa	Presence	Location	Description	Images
†Altirhinus	Aptian-Albian	Khukhtek Formation, Mongolia		Atlascopcosaurus Dollodon Iguanodon Lurdusaurus Mantellisaurus Ouranosaurus Tenontosaurus tilletti Theiophytalia
†Atlascopcosaurus †Atlascopcosaurus loadsi	Aptian/Albian	Eumeralla Formation, Victoria, Australia	2-to-3-metre (7-to-10-foot) long hypsilophodont
†Changchunsaurus †Changchunsaurus parvus		Quantou Formation, Jilin, China	As a small basal ornithopod, Changchunsaurus would have been a swift bipedal herbivore, feeding close to the ground.
†Dollodon †Dollodon bampingi	Barremian-?Aptian	Bernissart, Belgium; ?England; ?Germany	A lightly constructed iguanodont, about 6 metres (20 feet) long, estimated to weigh about 1 tonne (1 long ton; 1 short ton)
†Equijubus †Equijubus normani		Mazong Shan, Gansu, China	Primitive hadrosaur or iguanodont
†Iguanodon †Iguanodon bernissartensis		Europe	Worldwide distributed, type genus of the Iguanodontia. 10 metres (33 feet) long
†Lurdusaurus †Lurdusaurus arenatus		Niger	9-metre (30-foot) long heavily built Iguanodont
†Mantellisaurus †Mantellisaurus atherfieldensis		Atherfield, England, UK	formerly known as Iguanodon atherfieldensis
†Osmakasaurus †Osmakasaurus depressus		Lakota Formation, South Dakota, USA	A genus intermediate between Camptosaurus and more derived iguanodonts.
†Ouranosaurus †Ouranosaurus nigeriensis		Echkar Formation, Niger	7-metre (23-foot) long hadrosauroid, possibly with a sail on the back
†Planicoxa †Planicoxa venenica		Cedar Mountain Formation, Utah	A genus of advanced iguanodont
†Qantassaurus †Qantassaurus intrepidus		Victoria, Australia	1.8-metre (6-foot) long hypsilophodontid
†Siluosaurus †Siluosaurus zhanggiani		Xinminbao Group, Gansu, China	A hypsilophodontid or other basal ornithopod, Siluosaurus would have been a bipedal herbivore.
†Tenontosaurus †Tenontosaurus tilletti †Tenontosaurus dossi		Cloverly Formation, Wyoming and Montana, Antlers Formation, Oklahoma, Twin Mountains Formation, Texas, USA	8-metre (26-foot) long early iguanodont
†Theiophytalia †Theiophytalia kerri	Aptian to Albian	Purgatoire Formation, Colorado, USA	An iguanodont described as intermediate in derivation between Camptosaurus and Iguanodon
†Zephyrosaurus †Zephyrosaurus schaffi		Cloverly Formation, Montana, USA	Hypsilophodont

†Plesiosaurs

†Plesiosaurs of the Aptian
Taxa	Presence	Location	Description	Images
†Callawayasaurus †Callawayasaurus colombiensis		Paja Formation, Colombia	8-metre (26-foot) long elasmosaurid	Kronosaurus Umoonasaurus
†Kronosaurus †Kronosaurus boyacensis	Aptian to Albian	Boyaca, Colombia	Among the largest pliosaurs, body-length estimates put the total length of Kronosaurus at 9 to 10 metres (30 to 33 feet)
†Sinopliosaurus †Sinopliosaurus weiyuanensis	Aptian to Albian	China	Possibly a pliosauroid.
†Umoonasaurus †Umoonasaurus demoscyllus		Australia	Relatively small cryptocleidid, around 2.5 metres (8 feet) long, identified by the three crest-ridges on its skull.

†Pterosaurs

†Sauropods

†Sauropods of the Aptian
Taxa	Presence	Location	Description	Images
†Amazonsaurus †Amazonsaurus maranhensis		Itapecuru Formation, Maranhão, Brazil	A genus of 12 metres (39 feet) long diplodocoid.	Malawisaurus Nigersaurus Sauroposeidon
†Cedarosaurus †Cedarosaurus weiskopfae		Cedar Mountain Formation, Utah; Paluxy Formation, Texas	A brachiosaurid
†Fusuisaurus †Fusuisaurus zhaoi		Napai Formation, Guangxi, China	Probably a basal titanosaur, known by fragmentary postcranial remains
†Karongasaurus †Karongasaurus gittelmani		Malawi	Titanosaurid which fossils consist solely of parts of a lower mandible and a few teeth
†Ligabuesaurus †Ligabuesaurus leanza		Argentina	A basal titanosaurid
†Malawisaurus †Malawisaurus dixeyi		Malawi	One of the few titanosaurs for which skull material has been found
†Nigersaurus †Nigersaurus taqueti		Elrhaz Formation, Niger	Diplodocoid dinosaur, one of the most common genera found in the rich fossil vertebrate fauna of the Elrhaz Formation
†Paluxysaurus †Paluxysaurus jonesi		Twin Mountains Formation, Texas, USA	A basal titanosauriform
Phuwiangosaurus		Sao Khua Formation, Thailand
†Sauroposeidon †Sauroposeidon proteles		Antlers Formation, Oklahoma, USA	The last known giant brachiosaurid; extrapolations indicate that the head of Sauroposeidon could reach 17 metres (56 feet) in height, making it the tallest known dinosaur. With an estimated length of 30 metres (98 feet) and a mass of 36 to 40 tonnes (35 to 39 long tons; 40 to 44 short tons) it also ranks among the longest and heaviest.
†Tangvayosaurus †Tangvayosaurus hoffeti		Grès Supérior Formation, Laos	A basal titanosaur, known from the remains of two or three individuals.
†Venenosaurus †Venenosaurus dicrocei		Cedar Mountain Formation, Utah, USA	A titanosaur, known from an incomplete skeleton of an adult and a juvenile

†Stegosaurs

†Stegosauria of the Aptian
Taxa	Presence	Location	Description	Images
†Wuerhosaurus †Wuerhosaurus homheni †Wuerhosaurus ordosensis		Xinjiang, Inner Mongolia, China	7-metre (23-foot) long stegosaurid	Wuerhosaurus

†Non-Avian Theropods

†Non Avian Theropods of the Aptian
Taxa	Presence	Location	Description	Images
†Acrocanthosaurus †Acrocanthosaurus atokensis		Texas, Oklahoma, ?Maryland, USA	Likely an apex predator, up to 12 metres (39 feet) long. Classification disputed (Carcharodontosaurid or Allosaurid)	Acrocanthosaurus Deinonychus Genyodectes Huaxiagnathus Kryptops Neovenator Protarchaeopteryx Sinornithoides Sinosauropteryx Suchomimus Tyrannotitan Utahraptor
†Beipiaosaurus		Yixian Formation
†Deinonychus †Deinonychus antirrhopus		Cloverly Formation, Montana and Wyoming, Antlers Formation, Oklahoma, Potomac Formation, Maryland, USA	3-to-4-metre (10-to-13-foot) long carnivorous dromaeosaurid
†?Genyodectes †Genyodectes serus		Chubut Province, Argentina	Possibly ceratosaurian
†Huaxiagnathus †Huaxiagnathus orientalis		Yixian Formation, Liaoning, China	Large (1.8 metres (6 feet) long) compsognathid
†Kakuru †Kakuru kujani		Marree Formation, South Australia, Australia	A little-known maniraptoran known primarily from a single fossilized tibia, which had been fossilized through a rare process in which the bone through hydration turned to opal. Apart from the tibia, the first find included some small probable fibula fragments. Later a foot digit was referred that might have come from the same species, but the assignment is dubious. The tibia is broken into about ten larger pieces and roughly 33 centimetres (13 inches) long. It is very slender in build and shows the impression of the ascending process of the astragalus, an ankle bone itself lost. The process seems to have been very long and narrow. Kakuru is believed to have been carnivorous, was bipedal and about 2 to 3 metres (7 to 10 feet) in length. This small dinosaur seems to have had long, slender legs.
†Kryptops †Kryptops palaios		Elrhaz Formation, Niger	Earliest-known abelisaurid
†Microraptor †Microraptor gui		Jiufotang Formation, Liaoning, China	Small (90 centimetres (35 inches) long) feathered dromaeosaurid, possibly the same species as Microraptor zhaoianus
"†Nanshiungosaurus" bohlini	Barremian-Aptian	Upper Xinminbao Group	A species of relatively large therizinosaur dinosaur measuring around 6 meters long and 1.3 tonnes heavy. Due to the lack of shared unique traits and the large age difference with the slightly smaller Nanshiungosaurus brevispinus, it is generally considered that "Nanshiungosaurus" bohlini is unrelated to the previous and might warrant its own genus.
†Neovenator †Neovenator salerii		Isle of Wight, England, UK	7.5-metre (25-foot) long allosauroid
†Protarchaeopteryx †Protarchaeopteryx robusta		Yixian Formation, Liaoning, China	Primitive oviraptosaur, possibly synonymous with Incisivosaurus
†Similicaudipteryx †Similicaudipteryx yixianensis		Jiufotang Formation, Liaoning, China	Caudipterid oviraptosaur
†Sinornithoides †Sinornithoides youngi		China	1-metre (3-foot) long troodontid
†Sinosauropteryx †Sinosauropteryx prima		Liaoning, China	1.2-metre (4-foot) long compsognathid, fossilized with traces of color pigmentation in its feathers
†Sinotyrannus †Sinotyrannus kazuoensis		Jiufotang Formation, Liaoning, China	A species of large basal proceratosaurid tyrannosaur, reaching a total estimated length of 7.5–10 m and a maximum weight of 1.2-2.5 tonnes.
†Suchomimus †Suchomimus tenerensis		Tenere, Niger	12-metre (39-foot) long spinosaurid
†Tyrannotitan †Tyrannotitan chubutensis		Chubut Province, Argentina	12-metre (39-foot) long carcharodontosaurid
†Utahraptor^[5] †Utahraptor ostrommaysorum		North America	The largest known dromaeosaurid
†Xiongguanlong †Xiongguanlong baimoensis	Aptian	Yixian Formation, China	A medium sized tyrannosauroid and a close relative of the later Alectrosaurus and eutyrannosaurian tyrannosaurs.
†Yutyrannus †Yutyrannus huali	Aptian	Yixian Formation, China	A 9-metre (30-foot) tyrannosauroid and the largest dinosaur with feathers preserved

References

Notes

^ Gradstein et al. (2004)
^ Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta; Premoli Silva, Isabella (2008-07-15). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)". Earth and Planetary Science Letters. 271 (1–4): 88–100. Bibcode:2008E&PSL.271...88L. doi:10.1016/j.epsl.2008.03.055.
^ Leckie, R.; Bralower, T.; Cashman, R. (2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous" (PDF). Paleoceanography. 17 (3): 1–29. Bibcode:2002PalOc..17.1041L. doi:10.1029/2001pa000623.
^ Archangelsky, Sergio. "The Ticó Flora (Patagonia) and the Aptian Extinction Event." Acta Paleobotanica 41(2), 2001, pp. 115-22.
^ Mortimer, Mickey. "List of Dromaeosaurids". Archived from the original on October 3, 2011. Retrieved July 8, 2011.

Literature

Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
d'Orbigny, A.C.V.M.; 1842: Paléontologie française: Terrains crétacés, vol. ii. (in French)

External links

GeoWhen Database - Aptian
Mid-Cretaceous timescale, at the website of the subcommission for stratigraphic information of the ICS
Stratigraphic charts of the Lower Cretaceous: [1] and [2], at the website of Norges Network of offshore records of geology and stratigraphy

[1] Gradstein et al. (2004)

[2] Li, Yong-Xiang; Bralower, Timothy J.; Montañez, Isabel P.; Osleger, David A.; Arthur, Michael A.; Bice, David M.; Herbert, Timothy D.; Erba, Elisabetta; Premoli Silva, Isabella (2008-07-15). "Toward an orbital chronology for the early Aptian Oceanic Anoxic Event (OAE1a, ~ 120 Ma)". Earth and Planetary Science Letters. 271 (1–4): 88–100. Bibcode:2008E&PSL.271...88L. doi:10.1016/j.epsl.2008.03.055.

[oaedef-3] Leckie, R.; Bralower, T.; Cashman, R. (2002). "Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous" (PDF). Paleoceanography. 17 (3): 1–29. Bibcode:2002PalOc..17.1041L. doi:10.1029/2001pa000623.

[4] Archangelsky, Sergio. "The Ticó Flora (Patagonia) and the Aptian Extinction Event." Acta Paleobotanica 41(2), 2001, pp. 115-22.

[5] Mortimer, Mickey. "List of Dromaeosaurids". Archived from the original on October 3, 2011. Retrieved July 8, 2011.

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