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24-669: The Lisandro Formation , alternatively known as the Cerro Lisandro Formation , is a Late Cretaceous ( Late Cenomanian to Early Turonian ) geologic formation with outcrops in the Neuquén , Río Negro and Mendoza Provinces of Argentina . It is the youngest formation within the Río Limay Subgroup, the lowest section of the Neuquén Group . Formerly that subgroup was treated as a formation, and

48-653: A northward course towards Asia. In the Southern Hemisphere, Australia and Antarctica seem to have remained connected and began to drift away from Africa and South America. Europe was an island chain. Populating some of these islands were endemic dwarf dinosaur species. In the Late Cretaceous, the hadrosaurs , ankylosaurs , and ceratopsians experienced success in Asiamerica (Western North America and eastern Asia). Tyrannosaurs dominated

72-536: A sub-family of Pteranodontidae , Nesov (1984) named the Azhdarchinae to include the pterosaurs Azhdarcho , Quetzalcoatlus , and Titanopteryx (now known as Arambourgiania ). They were among the last known surviving members of the pterosaurs, and were a rather successful group with a worldwide distribution. Previously it was thought that by the end of the Cretaceous, most pterosaur families except for

96-536: A very different dinosaurian fauna, with most predators being abelisaurids and carcharodontosaurids ; and titanosaurs being among the dominant herbivores. Spinosaurids were also present during this time. Birds became increasingly common, diversifying in a variety of enantiornithe and ornithurine forms. Early Neornithes such as Vegavis co-existed with forms as bizarre as Yungavolucris and Avisaurus . Though mostly small, marine Hesperornithes became relatively large and flightless, adapted to life in

120-786: Is currently unnamed, recently discovered in Transylvania , may be the largest representative of the family thus far discovered. This unnamed specimen (nicknamed " Dracula " by paleontologists), currently on display in the Altmühltal Dinosaur Museum in Bavaria is estimated to have a wingspan of 12–20 m (39–66 ft), although similarities to the contemporary azhdarchid Hatzegopteryx have also been noted. Azhdarchids were originally classified as close relatives of Pteranodon due to their long, toothless beaks. Others have suggested they were more closely related to

144-479: Is it particularly evident that a true systematic decline was ever in place, especially with the discovery of smaller pterosaur species. Several old mammal groups began to disappear, with the last eutriconodonts occurring in the Campanian of North America . In the northern hemisphere, cimolodont , multituberculates , metatherians and eutherians were the dominant mammals, with the former two groups being

168-520: The Deccan Traps , both of which have been firmly dated to the time of the extinction event. In theory, these events reduced sunlight and hindered photosynthesis , leading to a massive disruption in Earth's ecology . A much smaller number of researchers believe the extinction was more gradual, resulting from slower changes in sea level or climate . Azhdarchidae Azhdarchidae (from

192-686: The Persian word azhdar , اژدر , a dragon-like creature in Persian mythology ) is a family of pterosaurs known primarily from the Late Cretaceous Period, though an isolated vertebra apparently from an azhdarchid is known from the Early Cretaceous as well (late Berriasian age, about 140 million years ago). Azhdarchids are mainly known for including some of the largest flying animals discovered, but smaller cat-size members have also been found. Originally considered

216-549: The "blunt-beaked" forms with shorter and deeper bills and the "slender-beaked" forms with longer and thinner jaws. It had been suggested azhdarchids were skimmers, but further research has cast doubt on this idea, demonstrating that azhdarchids lacked the necessary adaptations for a skim-feeding lifestyle, and that they may have led a more terrestrial existence similar to modern storks and ground hornbills . Most large azhdarchids probably fed on small prey, including hatchling and small dinosaurs; in an unusual modification of

240-930: The Azhdarchidae disappeared from the fossil record, but recent studies indicate a wealth of pterosaurian fauna, including pteranodontids , nyctosaurids , tapejarids and several indeterminate forms. In several analyses, some taxa such as Navajodactylus , Bakonydraco and Montanazhdarcho were moved from Azhdarchidae to other clades. Azhdarchids are characterized by their long legs and extremely long necks, made up of elongated neck vertebrae which are round in cross section. Most species of azhdarchids are still known mainly from their distinctive neck bones and not much else. The few azhdarchids that are known from reasonably good skeletons include Zhejiangopterus and Quetzalcoatlus . Azhdarchids are also distinguished by their relatively large heads and long, spear-like jaws. There are two major types of azhdarchid morphologies:

264-859: The Cretaceous Period derived from the German name Kreidezeit , and T is the abbreviation for the Tertiary Period (a historical term for the period of time now covered by the Paleogene and Neogene periods). The event marks the end of the Mesozoic Era and the beginning of the Cenozoic Era. "Tertiary" being no longer recognized as a formal time or rock unit by the International Commission on Stratigraphy ,

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288-850: The K-T event is now called the Cretaceous—Paleogene (or K-Pg) extinction event by many researchers. Non- avian dinosaur fossils are found only below the Cretaceous–Paleogene boundary and became extinct immediately before or during the event. A very small number of dinosaur fossils have been found above the Cretaceous–Paleogene boundary, but they have been explained as reworked fossils , that is, fossils that have been eroded from their original locations then preserved in later sedimentary layers. Mosasaurs , plesiosaurs , pterosaurs and many species of plants and invertebrates also became extinct. Mammalian and bird clades passed through

312-617: The Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Due to plate tectonics , the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia . India maintained

336-767: The Lisandro Formation was known as the (Cerro) Lisandro Member . The type locality of the Lisandro Formation is the hill known as Cerro Lisandro in Neuquén Province. This formation conformably overlies the Huincul Formation , and it is in turn overlain by the Portezuelo Formation , which is a part of the Río Neuquén Subgroup. The Lisandro Formation varies between 35 and 75 metres (115 and 246 ft) thick,

360-506: The azhdarchid bodyplan, the robust Hatzegopteryx may have tackled larger prey as the apex predator in its ecosystem. In another departure from typical azhdarchid lifestyles, the jaw of Alanqa may possibly be an adaptation to crushing shellfish and other hard foodstuffs. Azhdarchids are generally medium- to large-sized pterosaurs, with the largest achieving wingspans of 10–12 metres (33–39 ft), but several small-sized species have recently been discovered. Another azhdarchid that

384-524: The boundary with few extinctions, and evolutionary radiation from those Maastrichtian clades occurred well past the boundary. Rates of extinction and radiation varied across different clades of organisms. Many scientists hypothesize that the Cretaceous–Paleogene extinctions were caused by catastrophic events such as the massive asteroid impact that caused the Chicxulub crater , in combination with increased volcanic activity , such as that recorded in

408-664: The large predator niche in North America. They were also present in Asia, although were usually smaller and more primitive than the North American varieties. Pachycephalosaurs were also present in both North America and Asia. Dromaeosaurids shared the same geographical distribution, and are well documented in both Mongolia and Western North America. Additionally therizinosaurs (known previously as segnosaurs) appear to have been in North America and Asia. Gondwana held

432-636: The most common mammals in North America. In the southern hemisphere there was instead a more complex fauna of dryolestoids , gondwanatheres and other multituberculates and basal eutherians ; monotremes were presumably present, as was the last of the haramiyidans , Avashishta . Mammals, though generally small, ranged into a variety of ecological niches, from carnivores ( Deltatheroida ), to mollusc-eater ( Stagodontidae ), to herbivores (multituberculates, Schowalteria , Zhelestidae and Mesungulatidae ) to highly atypical cursorial forms ( Zalambdalestidae , Brandoniidae ). True placentals evolved only at

456-540: The numerous teleost fishes, which in turn evolved into new advanced and modern forms ( Neoteleostei ). Ichthyosaurs and pliosaurs , on the other hand, became extinct during the Cenomanian-Turonian anoxic event . Near the end of the Cretaceous Period, flowering plants diversified. In temperate regions, familiar plants like magnolias , sassafras , roses , redwoods , and willows could be found in abundance. The Cretaceous–Paleogene extinction event

480-407: The open sea. Though primarily represented by azhdarchids , other forms like pteranodontids , tapejarids ( Caiuajara and Bakonydraco ), nyctosaurids and uncertain forms ( Piksi , Navajodactylus ) are also present. Historically, it has been assumed that pterosaurs were in decline due to competition with birds, but it appears that neither group overlapped significantly ecologically, nor

504-577: The thinnest of the three formations in its subgroup. It is composed of siltstones and claystones , red in color, which have been interpreted as a swampy to fluvial environment . Usually, the red Lisando Formation rocks are easy to distinguish from the greenish or yellowish deposits of the Huincul Formation. Not many dinosaurs are represented in the Lisandro Formation; other types of animals are frequently found. Fossils documented from this formation are: Late Cretaceous During

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528-640: The toothy ctenochasmatids (which include filter-feeders like Ctenochasma and Pterodaustro ). Currently it is widely agreed that azhdarchids were closely related to pterosaurs such as Tupuxuara and Tapejara . Classification after Unwin 2006, except where noted. One of the most complete cladograms of azhdarchids is presented by Andres (2021): Azhdarcho Albadraco Aerotitan Mistralazhdarcho Phosphatodraco Aralazhdarcho Eurazhdarcho Zhejiangopterus Wellnhopterus Cryodrakon Hatzegopteryx Arambourgiania Quetzalcoatlus [REDACTED] In

552-433: The very end of the epoch; the same can be said for true marsupials . Instead, nearly all known eutherian and metatherian fossils belong to other groups. In the seas, mosasaurs suddenly appeared and underwent a spectacular evolutionary radiation. Modern sharks also appeared and penguin-like polycotylid plesiosaurs (3 meters long) and huge long-necked elasmosaurs (13 meters long) also diversified. These predators fed on

576-537: Was a large-scale mass extinction of animal and plant species in a geologically short period of time, approximately 66  million years ago (Ma). It is widely known as the K–T extinction event and is associated with a geological signature, usually a thin band dated to that time and found in various parts of the world, known as the Cretaceous–Paleogene boundary (K–T boundary). K is the traditional abbreviation for

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