Вернусь к вопросу вымирания боргиенид. Почему-то он мало кого заинтересовал. Пишут, что их вытеснили енотовые, которые попали в Ю.Америку в конце миоцена. Когда окончательно вымерли спарассодонты (кроме тилакосмила)?

Я думаю, что спарассодонты практически вымерли к началу плейстоцена. Проциониды их вытеснили. Только тилакосмил выжил, что объясняется его специализацией.

"Все таки это не слишком специализированные хищники, разве что развитием нервной системы превосходящие боргиен."
Вот именно, для того, чтобы вытеснить боргиенид хватило и не очень специализированных хищников. Главное, что у них были хорошо развитые мозги. К тому же проциониды могли приложить руку (ну или лапу) к исчезновению части травоядных, которые привыкли к медлительным недалёким хищникам, коими и были боргиениды.

Ну раз боргиениды так повально вымерли, значит они были неспособны конкурировать с проционидами. А вообще мы наверное плохо знаем южноамериканских миоцен-плиоценовых проционид. Наверное не все они напрминали современных енотов (вспомните хотя бы хапалмаланию).

"Вот потом в Юж. Америку проникли действительно опасные и эффективные хищники - тремарктоидные медведи, смилодоны, прочие кошачьи, крупные псовые."
Проциониды были вестниками армагеддона.

Эргастер, но ведь они не могли просто так угаснуть, что копытные, что боргиениды. Должна была быть причина. Условия среды там менялись? Кстати, частичную конуренцию травоядным могли оказать и прибывшие грызуны. Хотя грызущий нотоунгулят мезотерий дожил до плейстоцена, рядом с разнообразными грызунами. Чё-то там непонятное творилось в этой Южной Америке...

Интересно, обе Америки соединялись в миоцене? Центральная Америка "всплывала"?

А на север пробрались первые мегаленивцы и кавиамофные грызуны.

спасибо)
скачиваю.

Вес проборгиены определяют в 600 кг.

А тилакосмила в 150 кг! Наверное имелось в виду минимальный вес мелкой самки мегистотерия и максимальный вес очень крупных самцов тилакосмила:-)
Тилакосмил весом в 150 кг это как волк весящий 90 кг.

Time for more borhyaenoids. Finally, we get round to the taxa that you might have seen or read about in prehistoric animal books: the sabre-toothed thylacosmilids, the supposedly bear-like borhyaenids, and the gigantic and even more bear-like proborhyaenids. We previously looked at basal borhyaenoids here, and at the mostly scansorial, mustelid-like hathlyacinids and prothylacinids here. Here we go... 

We begin with the borhyaenids (yes, borhyaenid borhyaenoids), a group of about ten genera of superficially dog- or thylacine-like borhyaenoids. The oldest (Nemolestes) is from the Early Eocene or possibly Late Palaeocene while the youngest (Eutemnodus and Parahyaenodon) are from the Early Pliocene (Marshall 1978). Easily the best known member of the group is Borhyaena tuberata from the Santacrucian (= Early Miocene), and it's like its contemporary Cladosictis in being frequently depicted in the popular and semi-technical literature. As was also the case with Cladosictis, its 'conventional' image is - so it turns out - pretty far off the mark. 


The best known life restoration of this animal (that produced by John Long for Mammal Evolution: An Illustrated Guide) depicts it as something like a long-tailed bear, and I had always thought that Borhyaena was giant, and perhaps similar in size to a brown bear. In fact, weight estimates (Argot 2003) put it at 19-29 kg, which is about equivalent to a small hyaena or wolf, or a large thylacine. However, its robust skull, with its particularly broad zygomatic arches, indicate a disproportionately large amount of skull and neck musculature, and mass estimates for the whole animal based on skull proportions alone (and assuming body proportions resembling those of extant carnivorous mammals) give Borhyaena an inflated mass of 74 kg (vividly illustrating why knowing the overall proportions of an animal are important when estimating its weight: Van Valkenburgh 1985, 1987). The substantial neck musculature indicates an ability to carry heavy loads.

A semi- or fully digitigrade manus, short, blunt claws, and forelimbs that were restricted to parasagittal movement and exhibit reduced distal musculature indicate that Borhyaena was terrestrial and cursorial - and, in fact, the most cursorial of all borhyaenoids - but its limbs weren't as proportionally elongate as those of extant cursorial predators. However, that might not have been such a problem, because virtually all the potential large-bodied prey (an incredible assortment of xenarthrans, astrapotheres, notoungulates and big rodents) were not cursorial either (in the Santacrucian fauna, only proterotheriid and macraucheniid litopterns can be considered cursorial) (Argot 2004a). While previously depicted as being plantigrade, what is known of ankle morphology and forelimb proportions show that Borhyaena was more likely digitigrade in the hindlimb (Argot 2003: life restoration and skeletal reconstruction above © C. Argot). 
Whether the other borhyaenids were like 'new-look Borhyaena' remains to be shown.
Proborhyaenids have usually been thought of as hyaena-like or bear-like, while thylacosmilids are well known for being strongly convergent with sabre-toothed cats. While Marshall (1977) thought that proborhyaenids might be the most basal of borhyaenoids (while at the same time the most specialised), it has more recently been argued that proborhyaenids and thylacosmilids share a number of derived characters and are hence sister-taxa (Muizon 1994, 1999, Babot et al. 2002). One of the most interesting characters present in both proborhyaenids and thylacosmilids is the presence of ever-growing, open-rooted upper canines. Both groups also exhibit strongly projecting occipital condyles, indicating that they were capable of greater rotation and movement at the head-neck joint than other borhyaenoids. Babot et al. (2002) suggested that the presence of fine ridges and grooves on the canine roots might be diagnostic for proborhyaenids, but the fact that thylacosmilids have such strongly modified canines raises the possibility that thylacosmilids had this character ancestrally but later reversed it. 
Proborhyaenids are unique to the Eocene and Oligocene: there are only four recognised genera (Callistoe, Arminiheringia*, Paraborhyaena and Proborhyaena), and Proborhyaena in particular has often been referred to as huge and bear-like, with there being estimates here and there of skulls perhaps 60 cm long [P. gigantea holotype lower jaw shown here, from Patterson & Marshall (1978). From top to bottom, the specimen is shown in labial, occlusal and lingual views. Scale bar = 50 mm]. However, as has turned out to be the case for other archaic carnivorous mammals (like the hyaenodontids), big, bear-sized skulls do not necessarily mean big, bear-sized bodies, and an articulated proborhyaenid skeleton (read on) shows that these animals had big heads for their size. 
As is the case with most borhyaenoid genera, proborhyaenids are mostly known from fragmentary jaws and other parts of skulls, but in 2002 a near-complete proborhyaenid skeleton [shown above: from Babot et al. (2002). Scale bar = 100 mm], representing the new taxon Callistoe vincei, was described from the Casamayoran (= Early Eocene) Lumbrera Formation of Salta, Argentina (Babot et al. 2002). The generic name comes from Callisto, the Arcadian nymph loved by Zeus and changed by him into a bear to protect her from Hera's wrath (Jupiter has a moon called Callisto). In contrast to the other proborhyaenids, Callistoe has a gracile, narrow snout and might have superficially resembled a thylacine in facial shape. 
Arminiheringia had unusual procumbent lower canines: there has actually been some disagreement as to whether this is natural or not (Bond & Pascual 1983), but it does appear to be according to Babot et al. (2002) (A. auceta shown here, from Simpson 1932). Paraborhyaena also had somewhat procumbent lower canines. After Thylacosmilus, Simpson (1932) regarded Arminiheringia auceta (one of three species in the genus) as the most specialised borhyaenoid, and also one of the largest, 'about the size of the great Pharsophorus lacerans' (Pharsophorus is a borhyaenid). Exactly how big Pharsophorus was, however, I have no idea - and was it supposed to be bigger than, say, Proborhyaena?
Finally, we come to the superficially cat-like thylacosmilids, the only borhyaenoid group that are at all familiar, and all thanks to the incredible Thylacosmilus atrox Riggs, 1933 of the Late Miocene and Early Pliocene of Catamarca, north-western Argentina. In contrast to all other borhyaenoids, thylacosmilids were short-faced and had a complete bony postorbital bar (although not all did - read on). T. atrox is the only thylacosmilid we ever hear about, but it isn't the only one. 
Achlysictis Ameghino, 1891, known only from mandibular fragments and teeth (three species have been named), was smaller than T. atrox and differed from it in tooth cusp characters. Similar comments can be made about Hyaenodonops Ameghino, 1908, known only from teeth (though postcrania has been referred to it). Notosmilus Kraglievich, 1960, named for a maxilla and canine, was only about half the size of T. atrox. Marshall (1976) regarded all of these taxa as distinct, but Goin & Pascual (1987) and McKenna & Bell (1997) regarded them all as synonyms of Thylacosmilus. Of course, if that's true, then the generic name Thylacosmilus is predated by both Achlysictis and Notosmilus and the ICZN would have to be petitioned if we want to preserve Thylacosmilus (which we do). Incidentally, Riggs (1933) named a second species of Thylacosmilus, T. lentis, but it was argued by Marshall (1976) to be synonymous with T. atrox. Most recently, Goin (1997) named the Middle Miocene species Anachlysictis gracilis from the La Venta site in Colombia. This animal differed from the other thylacosmilids in smaller size, in possessing a flattened skull roof, and in lacking a postorbital bar.

Интересно, судя по зубам протилацион - суперхищник, крайне редко поедающий падаль и почти не грызучий кости.

http://s001.radikal.ru/i193/1001/e0/ddb4be6d5d36.jpg - два разных черепа а подписаны одинаково.