The largest rodent that ever lived weighed a ton or two, scientists revealed today.
The extinct mouse-like critter was larger than a bull.
An amateur paleontologist discovered the exceptionally well-preserved 20-inch-long fossil skull of the gargantuan rodent — dubbed Josephoartigasia monesi — embedded in a boulder on a beach in Uruguay. Scientists estimate this creature lived roughly 4 million years ago in South America, alongside terror birds, saber-toothed cats, giant sloths and massive armored mammals.
J. monesi weighed roughly 2,600 pounds on average, perhaps reaching up to 5,700 pounds.
Until this discovery, the largest known fossil rodent was Phoberomys, which might have weighed between 900 and 1,500 pounds when alive. In comparison, the largest rodent alive today — the capybara (Hydrochoerus hydrochaeris) of South America — weighs about 130 pounds.
"Imagine a mouse with the body weight of two race horses — it's very impressive indeed," researcher Ernesto Blanco, a biomechanicist at the Uruguayan Institute of Physics in Montevideo, told LiveScience.
The skull of the extinct rodent suggests it had weak chewing muscles, and its grinding teeth are very small. This suggests it might have eaten soft vegetation and perhaps fruit. Nearby fossils suggest it dwelled in forests in a river delta or near an estuary.
Although the rodent's chewing muscles may not have been strong, the researchers hope to reconstruct its head muscles to see if it had a strong bite. "All rodents have powerful bites, but this giant one's probably was terrific!" Blanco said.
The scientists will detail their findings online Jan. 16 in the journal Proceedings of the Royal Society B.
译文:
体型赛公牛的。。。老鼠
科学家今天揭露，史上体型最大的啮齿类动物重约一到两吨。
这种已经灭绝的，长得类似于老鼠的生物比公牛还大。
一个业余古生物学家发现一个保存异常完好的庞大啮齿类动物长达20英寸的头骨化石--它被命名为Josephoartigasia monesi--嵌在乌拉圭海滩边的一块石头里。科学家们估计该生物大约生活在400万年前的南美，和恐怖的鸟、马刀齿猫、巨大的树懒和魁梧的披甲类哺乳动物一同生活。
J. monesi平均约重2600磅，最终可能达5700磅。
在它被发现前，已知的最大的啮齿类化石动物为Phoberomys，它在活着时候大约重900到1500磅。比较一下，现存的世界上最大的啮齿类动物--南美的水豚（Hydrochoerus hydrochaeris）--重约130磅。在蒙得维的亚的乌拉圭物理学会的生物技师，研究人员Ernesto Blanco告诉LiveScience：“想象一下，一只老鼠有着两匹马的重量--真的让人印象深刻。”
从这个已经灭绝的啮齿类动物的头骨看出它咀嚼肌的能力很弱，磨齿很小。这就暗示它可能靠食用柔软的植物，或是水果为生。它旁边的化石则说明它生活在一个河流三角区域或靠近河口的一个森林中。
虽然该啮齿动物咀嚼肌不是很强，但是研究人员希望能重塑它的头部肌肉，以弄清它是否有很强的咀嚼能力。Blanco说：“所有的啮齿类动物都有强有力的咀嚼力，但是这个大家伙可能不太一样！”
科学家们将在1月16日在线发行的《皇家学会学报B》上详细叙述他们此次的发现。