Caiuajara is an extinct genus of tapejarid pterosaur from the Late Cretaceous of Brazil. It is known from a single type species, Caiuajara dobruskii.

 In 1971, the labourers Alexandre Dobruski and his son João Gustavo Dobruski found pterosaur fossils in a field near Cruzeiro do Oeste in the south of Brazil, in the state of Paraná. The finds were in 2011 brought to the attention of paleontologists Paulo C. Manzig and Luiz C. Weinschütz.

 In 2014, the type species Caiuajara dobruskii was named and described by Paulo Manzig, Alexander Kellner, Luiz Weinschütz, Carlos Fragoso, Cristina Vega, Gilson Guimarães, Luiz Godoy, Antonio Liccardo, João Ricetti and Camila de Moura. The generic name refers to the geological Caiuá Group and the related genus Tapejara. The specific name honours the discoverers.

 The holotype, CP.V 1449, was found in a sandstone layer of the Goio-Erê Formation, the age of which is uncertain; it is perhaps dating from the Coniacian-Campanian, very roughly about eighty-five million years old. It consists of a partial skeleton including the skull, lower jaws, neck vertebrae and wing elements. Many hundreds of bones have been discovered, concentrated in several bone beds, and representing at least forty-seven individuals but probably many more. In the total assembly, all elements of the skeleton are present. The bones have been three-dimensionally preserved, not compressed, but are only rarely articulated. The individuals found are often juveniles; adult animals are much rarer, only represented by two skulls and three humeri. Good specimens have been assigned as paratypes, the more fragmentary ones have been referred.

 The paratypes are: CP.V 865: a snout, rear of the mandibula, right jugal, vertebrae, ribs and metatarsals; CP.V 867: a snout and limb bones; CP.V 868: a snout, wing elements and other postcrania; CP.V 869: a vertebral column, right arm, coracoid, breastbone, wing phalanges, belly ribs, pelvic elements and a right tighbone; CP.V 870: a shoulder girdle with the humeri; CP.V 871: a right shoulder girdle with right arm elements; CP.V 872: s partial skeleton including the skull, lower jaws, right arm, neck vertebrae and additional limb elements; CP.V 873: a snout and finger phalanges; CP.V 999: a partial skull; CP.V 1001: a slab with a partial skull, lower jaws and postcrania of at least three individuals; CP.V 1003: a partial skull and symphysis; CP.V 1004: a snout; CP.V 1005: a partial crested skull with the complete mandibula; CP.V 1006: a partial crested skull lacking the snout combined with postcrania; CP.V 1023: a snout and postcrania; CP.V 1024: a skull and postcrania of at least three juveniles; CP.V 1025: a thighbone; CP.V 1026: a thighbone; CP.V 1450: a slab containing at least fourteen juveniles; CP.V 2003: a skull with lower jaws and articulated wing elements; UEPG/DEGEO/MP-4151: a slab with two skulls and postcrania; and UEPG/DEGEO/MP-4152: a snout with postcrania.

 Most specimens are part of the collection of the Centro Paleontológico of the Universidade do Contestado.

 The largest individuals of Caiuajara had an estimated wingspan of 2.35 metres. The species had a large toothless head with, in adult individuals, an enormous shark fin-shaped crest on the snout.

 The describing authors established several distinguishing unique traits, autapomorphies. The tip of the snout is strongly oriented to below, at 142 to 149°, relative to the edge of the upper jaw. The rear ascending branches of the praemaxillae on their midline form an elongated bony rim projecting to below into the nasoantorbital fenestra, the large skull opening in the side of the snout. In the concave upper rear of the symphysis, the fronts of the lower jaws grown together, a rounded depression is present. The front outer edge of the quadrate shows a longitudinal groove. Below the front part of the nasoantorbital fenestra, a depression is present in the upper jaw edge.

 Additionally, Caiuajara shows an unique combination of traits that are themselves not unique. The lower edge of the eye socket is rounded. At a maximal occlusion, the gap between the upper and lower jaw is wider than with other tapejarines. The pteroid on its bottom surface shows a conspicuous depression lacking a pneumatic opening.

 Caiuajara was assigned to the Tapejaridae, more precisely the Tapejarinae. It shares several traits with the tapejarids, such as a crest running from the front snout to the back of the head; an elongated nasoantorbital fenestra occupying over 40% of total skull length; and a large boss on the front edge of the coracoid. A typical tapejarine trait is the down-turned snout tip. A cladistic analysis showed that Caiuajara is a possible sister species of Tupandactylus. In 2014, Caiuajara was the geologically youngest known tapejarid (aside from the possible tapejarid Bakonydraco galaczi) and also the most southern one known. This expansion of their known range was seen as an indication that tapejarids had a global distribution. Moreover, Caiuajara is the first pterosaur found in the south of Brazil.

 The habitat of Caiuajara was a desert with dunes. The layers in which the fossils were found had been deposited in a lake in the desert; probably the bones had been exposed at the surface around the lake for a time and were then by storms blown into it, eventually sinking to the bottom. Possibly the same storms caused many individuals to die together; this could also have been the result of droughts. A succession of layers shows that the lake was likely inhabited by the pterosaurs for a great length of time, although it is also possible they visited the lake during regular migrations. Fossil plants — tapejarids are often assumed to have been herbivores — have not been found, so there are no direct indications about the food source. Likewise, remains of invertebrates have not been discovered.

 The large concentrations of fossils, among pterosaurs very rare and only equalled by those found of the Argentine form Pterodaustro, were by the describers seen as proof of a gregarious lifestyle, Caiuajara living in colonies. The many specimens also allowed to determine a growth series, the first such an ontogenetic sequence for pterosaurs of which it is nearly certain that it really represented a single species. The age of the exemplars can be determined, not just from size but also by the degree of ossification, especially of the breastbone, the long bones and the wrist, and the fusion of the shoulder blade and coracoid into a scapulocoracoid. It showed that juvenile individuals, the smallest specimens of which have a wingspan of about sixty-five centimetres, generally had the same proportions as adults. Especially important is that their humeri are not proportionally smaller and their humeral deltopectoral crests, the attachments of the main flight muscles, are not less developed, attaining a size of 38 to 40% of the humeral shaft length. This suggests that they were precocial, taking wing almost as soon as they hatched; parental care must have been limited. This might have been typical of all derived pterosaurs. The snout crest however, strongly changed during growth. It became much taller and also much more steeply inclined, from about 115° to 90°. Although the snout as a whole also became more massive, the snout tip inclination relative to the jaw edge remained the same. At the back of the skull an additional projection developed. Furthermore the dentary crest on the lower jaw strongly increased in size. No specimens have been found lacking the snout crest, indicating that Caiuajara was in this respect not sexually dimorphic and casting doubt on the hypothesis that pterosaurs normally were.

 Удивительную находку сделали латиноамериканские палеонтологи на юге Бразилии. В отложениях мелового периода они раскопали настоящее кладбище птерозавров нового, неизвестного науке вида. Похоже, крупную колонию крылатых ящеров сгубила засуха, говорят ученые.

 Остатки по меньшей мере 47 животных всех возрастов – от самых маленьких до уже старых – были обнаружены в древних озерных отложениях у города Крузейро ду Уэсте (Cruzeiro do Oeste) в штате Парана. Это находка стала самой южной для представителей беззубой клады Tapejaridae на территории страны, поскольку обычно этих животных находят в северной части Бразилии. Озеро, ставшее последним приютом для огромной стаи ящеров, находилось в центре сухой и жаркой пустыни. При этом большинство остатков птерозавров известно из прибрежных или мелководных морских отложений, а число видов, которые обитали бы в глубине континентов, сильно ограничено пустынными условиями, отметили палеонтологи.

 Новых птерозавров назвали Caiuajara dobruskii. Как показали исследования, это были общительные, предпочитавшие держаться вместе животные. Размеры разных особей, найденных близ Крузейро ду Уэсте, варьируют от 0,65 до 2,35 метра в размахе крыльев. Судя по всему, все они принадлежали к одному виду и относятся к разным возрастным категориям. Благодаря этому палеонтологи получили уникальную возможность изучить процессы взросления птерозавров.

 Разница в строении молодых и более взрослых ящеров невелика и касается преимущественно гребня, украшавшего голову каюажар, говорят ученые. У молодых  животных гребень невысокий и образует острый угол с черепом, с возрастом его размеры увеличиваются, а угол приближается к прямому. Кроме того, похоже, что птенцы Caiuajara dobruskii умели летать уже в самом раннем возрасте. На мысль об этом ученых натолкнуло практически полное отсутствие различий в посткраниальном скелете взрослых ящеров и их детенышей.

 Все ископаемые остатки каюажар были найдены на раскопе общей площадью порядка 20 квадратных метров, в породах, датируемых верхнемеловым возрастом. По предварительным оценкам, это местонахождение может содержать остатки более чем сотни древних летающих ящеров. Вполне возможно, что птерозавры не только жили все вместе, одной большой колонией, но и летали дружной стаей, в которую входили разновозрастные особи. Любопытно, что почти на полсотни особей в местонахождении приходится лишь две-три взрослых. Остальные остатки принадлежат птенцам и подросткам, причем некоторые их кости были сломаны еще при жизни или, во всяком случае, до окаменения.

 Пока у ученых нет объяснения массовой гибели животных в этой колонии. "Причины смерти остаются неизвестными, хотя сходство с динозаврами, погибшими в результате засухи, просто поразительно, – рассказал ведущий автор исследования Пауло Манзиг из университета Контестадо. – Тем не менее, мы можем иметь дело с последствиями пустынной бури, убившей всех этих птерозавров".

 Согласно другой гипотезе, кладбище птерозавров находится на месте древнего оазиса, в котором каюажары жили на протяжении очень долгого времени. В таком случае сотня летающих ящеров не погибла одновременно, а их скелеты постепенно накапливались в этом местонахождении. Время от времени, в результате тех же пустынных бурь, расчлененные и частично сочлененных скелеты попадали на дно озера, где в конечном итоге и сохранились. Также возможно, что каюажары были мигрирующими птерозаврами, посещавшими этот оазис эпизодически. Так или иначе, палеонтологам удалось выделить три основных слоя, в которых накапливались скелеты ящеров. Их общая мощность составляет примерно один метр.

 Репродукции (1, 2, 3):

 Ископаемые останки (1, 2, 3, 4, 5):

Tags: Вымершие рептилии, Мел, авеметатарзалии, аждархойды, архозавроморфы, архозавры, диапсиды, монофенестраты, орнитохейройды, птеродактили, птерозавры, тапежариды

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