Hoppers, diggers, and hopping diggers

All living mammals (except humans) that have become true bipeds have adopted a very specific and specialized bounding form of bipedalism. Bipedal hopping results in a distinctive pelvic structure and this structure has similarities to specialized fossorial groups, implying that these disparate groups are incurring similar locomotor stressors in their respective modes of life.

Hoppers :

With regards to the pelvis, kangaroos seem to have adapted to a bipedal hopping way of life by changing elements of the pelvis such as the large pubis and ischium and the long narrow ilium.

They seem to share this pelvic morphology with other groups of unrelated mammal which also employ a bounding type of locomotion and also with groups that  are fossorial.

Pelvis of kangaroos and kin:

A boxy pelvis with well developed pubis, ischiopubic ramus and ischium. Also a long, narrow, almost pronglike ilium.

 

tree kangaroo

Some hopping rodents:

Springhare

jerboa

Diggers:

This morphology of the pelvis appears again in mammal groups which are highly fossorial. The elongated, winglike ilium, and an overall boxy pelvis formed by a robust pubis and ischium, implys that some of the same stresses inherent in flexing and extending the hip during the bound are also acting in an animal that extends the limb backword against a substrate (i.e. digging)

cape dune mole rat

Ground squirrel

Cane Rat

Muscles of the Pelvis:

Published knowledge of muscular and osteology of the pelvis and hind limb of macropods seem to be lacking, with the exception of Hopwood 1976.

According to Hopwood, the biceps femoris, obturator exertenis, gemmelli, and iliopsoas are all fleshy well-developed muscles with origins on the pelvis.

The biceps femoris, part of the hamstrings group, aids in knee flexion and hip extension and stabilizes the hip. The obturator externis and gemellus both help stabilize the hip joint during locomotion, and the iliopsoas group aids in flexion of the thigh.

(PAUL R. HOPWOOD AND REX M. BUTTERFIELD. The musculature of the proximal pelvic limb of the Eastern Grey Kangaroo Macropus major (Shaw) Macropus giganteus (Zimm). J. Anat. (1976), 121, 2, pp. 259-277 )

LENGTHS OF PELVIC ELEMENTS:

Ischium length has been correlated with locomotor mode in old world monkeys, being shorter in the leaping monkeys like the colobus (more acceleration), longer in the more terrestrial cercopithecines. A shorter ischium gives greater acceleration in the leap, while a longer ischium gives greater hamstring power.

(K. Steudel. 1981. Functional Aspects of Primate Pelvic Structure: A Multivariate Approach. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 55:399-410 )

While data on ishium and pubic length is lacking to non-existent outside of primates, the well-developed ischium and pubis in macropods, leaping rodents, and fossorial rodents, suggests a need for strong hamstring muscles and muscle power rather than fast acceleration.

Which absolutely begs the question:

Who would win a standing start, a kangaroo or a Bugatti Veyron Super Sport?

http://ru.wikipedia.org/wiki/%D0%A4%D0%B0%D0%B9%D0%BB:Skeleton_of_Cape_Dune_Mole_Rat.jpg

http://snakephotographer.com/?tag=jerboa

http://www.thefeaturedcreature.com/2010_11_28_archive.html#axzz24Kfgnq9j

(http://www.google.com/imgres?q=springhare+skeleton&hl=en&sa=X&qscrl=1&rlz=1T4TSNJ_enUS454US454&biw=1366&bih=641&tbm=isch&prmd=imvns&tbnid=2XLvbEHDcBAGzM:&imgrefurl=http://www.sagazone.co.uk/forums/post/3425893/&docid=eUSlSK2_6tmaaM&imgurl=http://upload.wikimedia.org/wikipedia/commons/9/92/SpringhaasSkelLyd.jpg&w=235&h=494&ei=eI81UJ7AHoiE8QT0vIGQAg&zoom=1&iact=hc&vpx=357&vpy=2&dur=343&hovh=326&hovw=155&tx=100&ty=131&sig=108734651755445499111&page=1&tbnh=133&tbnw=62&start=0&ndsp=20&ved=1t:429,r:1,s:0,i:80

(http://www.tree-kangaroo.net/tkInfo.html)

http://www.nhc.ed.ac.uk/index.php?page=24.134.165.255.266

http://www.flickr.com/photos/26485684@N08/2885093922/

http://www.zoology.wisc.edu/uwzm/collections.html

http://www.spcollege.edu/hec/vt/vtde/anatomy/3a.htm

http://vanat.cvm.umn.edu/run/plate3.html

http://www.rightpet.com/Small-exotic-mammalDetail/greater-cane-rat

(Hudson, Penny E.; Corr, Sandra A.; Payne-Davis, Rachel C.; Clancy, Sinead N.; Lane, Emily; Wilson, Alan M.Functional anatomy of the cheetah (Acinonyx jubatus) hindlimb Journal of Anatomy, Apr2011, Vol. 218 Issue 4, p363-374)

UW Radiology. http://www.rad.washington.edu/academics/academic-sections/msk/muscle-atlas/lower-body/obturator-externus

http://www.animalspot.net/gallery/kangaroo-pictures

http://www.museumofosteology.org/museum-exhibits/5/Adaptation-Locomotion.htm

You can’t choose your family…the LCA of synapsids and sauropsids

Mammals are the only surviving members of the synapsids, a group that split from the sauropsids, which includes all of the groups that we think of as “reptiles” as well as dinosaurs, birds, and crocodilians. This split happened sometime around 300 MYA at the beginning of the Permian.

Traditional phylogenies place the oldest split within the sauropsids between the anapsids,  which include the modern day turtles and tortoises, from the diapsids which includes basically everything else reptilian, dinosaurish or bird. So if you’re a (living) sauropsid, either you are a turtle/tortoise, or you’re everybody else.

However! – recent phylogenies of turtles place them as the sister group to archosaurs (crocodiles and birds). In other words they are firmly in the middle of the diapsid group. This would change the phylogeny so that the earliest sauropsid split was between the lizards/snakes (squamates) and everything else reptilian (including birds). This seems to be the current consensus among paleontologists, so I’ll go with it.

So what would the last common ancestor of synapsids and sauropsids have looked like? We don’t know and probably never will know the actual LCA of these two groups, so all we can do is look at the fossils we have closest to this boundary.

The earliest known anapsid was Paleothyris  (notice, no holes behind the eye socket):

Paleothyris

The earliest know diapsid is Petrolacosaurus (notice, two holes in skull)

Petrolacosaurus

The relationships of the earliest synapsids, and sauropsids for that matter, are far from resolved. In other words, it’s still a mess… However it seems that the earliest synapsids were the pelycosaurs, including the groups Caseidae and the Ophiacodontidae.

Some of the earliest synapsids that we know of are Ophiacodon and Casea. (Note the single hole in the skull behind the eye socket.)

Ophiacodon

Casea

Casea might have looked remarkably like a marine iguana – though of course it’s more closely related to mammals, not reptiles, and lizards arose much later out of the sauropsids.

Here’s a marine iguana anyways…

Its worth repeating that the last common ancestor or mammals and reptiles may not have looked like Paleothyris, Petrolacosaurus, Ophiacodon, Casea or any other fossils we have; at best they would be cousins of the modern mammal and reptile lines. It gives you a rough idea of how we (the mammals and reptiles) started though.

So if we could invent a time machine and go back to the late Carboniferous or early Permian, what might the LCA of ancestor of mammals and reptile look like? The LCA probably had a solid skull (no holes) and the synapsids and diapsids later developed one and two holes respectively. It would have had the primitive (again ancestral) “reptile” jaw, with the articular meeting the dentary. The posture would have been sprawling, probably with short heavy legs. You may have started to see the teeth differentiate – some longer than others.

As an aside, even in the modern day sauropsids you see some groups with slightly different teeth – crocodiles.

 According to Merck at the UM Dept. Geology the basal amniotes did have this kind of rudimentary tooth differentiation, kind of proto-canines. You can see it in Paleothyris, the earliest anapsid, Petrolacosaurus, the earliest diapsid, and Ophiacodon, an early synapsid. This trait seems to be imbedded deep in the roots of these two groups.

Michael J. Benton. Phylogeny of the major tetrapod groups: Morphological data and divergence dates. 1990. Journal of Molecular Evolution, Volume 30, Issue 5, pp 409-424.

J. CUBO,F.PONTON,M.LAURIN,E.DE MARGERIE, AND J. CASTANET. Phylogenetic Signal in Bone Microstructure of Sauropsids. 2005. Syst. Biol. 54(4):562–574

Michael J. Donoghue, et al. 1989. THE IMPORTANCE OF FOSSILS IN PHYLOGENY RECONSTRUCTION. Annu. Rev. Ecol. Syst. 20:431-60

SE EVANS. 1988. The Upper Permian reptile Adelosaurus from Durham. Paleontology. Vol 31:957-964.

Sudhir Kumar & S. Blair Hedges. 1998.A molecular timescale for vertebrate evolution. NATURE| VOL 392 | 30

J.S. Rest, et. al. 2003. Molecular systematics of primary reptilian lineages and the tuatara mitochondrial genome. Molecular phylogenetics and evolution. 29:287-297.

ROBERT R. REISZ. 1977. Petrolacosaurus, the Oldest Known Diapsid Reptile. Science Vol. 196 no. 4294 pp. 1091-1093

CHRISTIAN A. SIDOR. 2001. SIMPLIFICATION AS A TREND IN SYNAPSID CRANIAL EVOLUTION. Evolution, 55(7), pp. 1419–1442

Michael S. Y. Lee. 2001. Molecules, morphology, and the monophyly of diapsid reptiles. Contributions to Zoology, 70 (1)

Rafael Zardoya · Axel Meyer. 2001. The evolutionary position of turtles revised. Naturwissenschaften 88:193–200.

Exposed Planet. http://exposedplanet.com/marine-iguana-relaxing-in-the-sun-galapagos-islands/

http://ib.berkeley.edu/courses/ib173/lectures/lecture1/173_lecture1.html

Paleos.com http://palaeos.com/vertebrates/synapsida/ophiacodontidae.html

Paleos.com http://palaeos.com/vertebrates/diapsida/araeoscelida.html

Paleos.com http://palaeos.com/vertebrates/eureptilia/protorothyrididae.html

University of Maryland Dept. of Geology. http://www.geol.umd.edu/~jmerck/nature/specimens/htmls/ophiacodon70887.html

123RF Stockphotos. http://www.123rf.com/photo_9489149_marine-iguana-couple-walking-on-white-beach-on-galapagos-islands.html

Archive.org. http://www.arkive.org/american-crocodile/crocodylus-acutus/image-G12846.html

Planet Dinosaur. http://planetdinosaur.com/Paleothyris.aspx

Encephalization quotients (EQ) in vertebrate animals

Intelligence is notoriously difficult to measure even in other people, let alone other species. One method commonly used, the encephalization quotient or EQ, is an equation comparing the proportional brain size of an animal, that is brain size relative to body size, to the “expected” brain size in an animal of that size. EQ greater than one indicates brain size larger than expected for an animal of this mass, if EQ equals one brain size is about average, if EQ less than one brain size is less than would be expected. The assumption being that proportional brain size of an animal is a general indicator of intelligence.

Definition of EQ:

“The encephalization quotient (EQ) expresses the ratio of

the actual brain size to the expected brain size for an animal

of a given mass . It shows whether the relative brain mass

is greater than (EQ>1), average (EQ=1), or less than

expected (EQ<1) for its body mass. “(Ari)

If you want to get technical:

“…defined by the allometric function for brain:body relations initially proposed by Snell (1892) in the form of E = kPα, where E and P are brain and body weights, respectively, and k and α are constants. For example, a taxon with an EQ of 6, the actual value calculated by Jerison for humans, would have a brain six times larger than that in the “average” mammalian taxon.” (Northcutt)

Of course brain size is affected by many different factors besides cerebral development. Species that have complex behaviors such as specialized foraging behaviors and/or those that echolate, such as bats, have brains larger than expected but don’t seem especially brainy. The theory being that more brain is required to process complex information when echolating in a three-dimensional environment. (Eisenburg) Also smaller animals such as mice tend to have proportionally larger brains than do larger animals. For example a mouse brain and human brain are both 1/40th of body weight, giving both an equal EQ, but no one would argue that a mouse is as intelligent as a human.

http://www.animalspot.net/

So EQ is pretty rough, but it does give some way of actually quantifying intelligence, and works pretty well as long as these extraneous factors are taken into account.

Sharks and fish with the highest EQ:

crocodile shark 2.92 – brainiest fish in the sea? like the thresher it lives at depth and its large eyes may have something to due with its large brain size. However they and threshers are members of the mackeral shark family which includes sharks like great whites and makos, which do seem pretty intelligent for sharks

bigeye thresher 1.58

whitetip 2.66,silky shark 1.83

skipjack tuna 1.31

(Lisnay)

Crocodile shark:

http://www.ecopacifico.org/ImagenesEspecies/Forms/AllItems.aspx

Marsupials:

virginianus 0.5 – not much upstairs…

marmosa 1.06, philander 1.09 – these marsupials may have relatively large brain sizes for marsupials perhaps due to the demands of arboreality

(eisenburg)

Monotremes:

monotremes EQ 0.87 – close to the mammal average

(Macrini)

Grey four-eyed oppossum (Philander)

http://animaldiversity.ummz.umich.edu/site/resources/pablo_goncalves/Philander_a.jpg/view.html

Cetaceans, pinnipeds, manatee and hippo:

hippo 0.3, manatee 0.4 – pretty dim, close to the average for ungulates

phoca 1.3-1.6, furseal 0.6, sealion 1.1 – close to average

dolphin 2.8, harbor porphoise 2.6, orca 1.5 – most intelligent of cetaceans? or is it echolocation affecting brain size?

sperm whale 0.3, , baleen whales 0.2 – don’t score well on EQ, close to hippos and manatees, which is interesting since hippos are the sister group to cetaceans; perhaps this is because baleen whales do not use echolocation and don’t have complex social groups

Harbour porpoise:

http://www.arkive.org/harbour-porpoise/phocoena-phocoena/

(Worthy)

Humans:

average modern human 5.28 – we’re pretty smart!

(Ruff)

Cave-art of Lascaux:

http://www.bradshawfoundation.com/lascaux/index.php

G.E.J. Worthy, J.P. Hickie. 1986.  Relative brain size in marine mammals. The american naturalist. 128:445-459.

J.F. Eisenburg and D.E. Wilson.  1981. Relative brain size and demographic strategies in didelphid marsupials.  The American Naturalist. 118:1-15.

T. J. LISNEY * AND S. P. COLLIN. Brain morphology in large pelagic fishes: a comparison between sharks and teleosts. Journal of Fish Biology (2006) 68, 532–554

C.B. Ruff, E. Trinkaus, and T.W. Holliday. Body mass and encephalization in pleistocene HOmo. 1997. Nature 387:173-176.

T.E. Macrini, T.Rowe, and M. Archer. Description of a Cranial Endocast From a Fossil Platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the Relevance of Endocranial Characters to Monotreme Monophyly. JOURNAL OF MORPHOLOGY 267:1000–1015 (2006)

Understanding Vertebrate Brain Evolution. R. Glenn Northcutt. Integr. Comp. Biol. (2002) 42 (4): 743-756

Inheritance and development of primitive Dinosaurian traits in the evolution of birds (Aves)

Premise:

If feathers and bipedality are the primitive condition in all basal dinosaurs, these traits would have been kept by saurischians  – theropods and sauropods – after the saurischian/ornithischian split, while ornithischians lost these primitive traits and became scaly and quadripedal. Selective pressures, whatever selected for these traits to continue in derived dinosaur groups, continued to push development of these traits from their primitive forms to a more derived state (flight and display feathers) in later theropods and birds. We would expect to see two signals in the fossil record:

A) at Saurischian/Ornithischian split, Ornithischians lost feather coverings and most bipedality while Saurischians retained these (at least as juveniles)

B) basal ornithischians should have these traits, lost in later groups

C) basal dinosaurs should have some sort of feather/integumentary structures and bipedality

Supporting evidence:

Evidence of feathers/proto-feathers/down in basal dinosaurs and derived theropods–

1. non-avian theropods Protoarchaeopteryx and Caudipteryx from upper jurassic/lower cretaceous (Qiang)

2. “filamentous integumentary structures” in early ornithischian Tianyulong of early cretaceous (144-90MYA) – first non-theropod feather structures/feathers occur before or near saurischia/ornithischia split (Zheng)

3. theropod Sinosauropteryx from lower jurassic, pubic impression with filaments impressions -structure most similar to down in ratites/ may have been covered in down to regulate temperature (Kundra)

4. Longisquama of late triassic 220 MYA shows feather impressions with similar structure to birds (Jones)

5. Anchiornis 150 MYA pennaceous and plumaceous feathers – pennaceous 1st evolved on distal forelimbs and tail, spreading to hind limbs- these were later lost and the forelimb and tail feathers developed (Hu)

http://www.geol.umd.edu/~tholtz/G104/lectures/104dinorise.html

Known basal dinosaurs and dinosauromorphs all bipedal—

1. Fruitadens (Butler; Zheng)

3. Eoraptor (Sereno’)  

Eoraptor

http://dinosaurs.about.com/od/dinosaurpictures/ig/Early-Theropod-Pictures/Eoraptor.htm

6. Herrerasaurus  (Butler; Zheng)

7. Massospondylous (Reisz)

Massospondylus

http://www.nenature.com/Dinosaurs/Massospondylus.htm

8. Coelophysis (Sullivan)

Mark Hallett Paleoart

http://www.bbc.co.uk/nature/life/Coelophysis

Xiao-Ting Zheng, Hai-Lu You2, Xing Xu3 & Zhi-Ming Dong. 2009. An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. Nature: Letters. 458:333-336.

MARTIN KUNDRA ´ T. 2004. When Did Theropods Become Feathered?Evidence for Pre-Archaeopteryx Feathery Appendages. JOURNAL OF EXPERIMENTAL ZOOLOGY. 302B:355–364

Terry D. Jones, John A. Ruben, Larry D. Martin, Evgeny N. Kurochkin, Alan Feduccia, Paul F. A. Maderson, Willem J. Hillenius,  Nicholas R. Geist, Vladimir Alifanov.  2000. Nonavian Feathers in a Late Triassic Archosaur. Science 288:2202-2205.

Dongyu Hu, Lianhai Hou, Lijun Zhang& Xing Xu. 2009. A pre-Archaeopteryx troodontid theropod from China with long feathers on the metatarsus. Nature: Letters 461:640-643.

Fucheng Zhang & Zhonghe Zhou. 2004. Palaeontology:  Leg feathers in an Early Cretaceous bird. Nature 431

Adam M. Yates and James W. Kitching. 2003. The earliest known sauropod dinosaur and the first steps towards sauropod locomotion. Proc. R. Soc. Lond. B 270: 1753-1758

T. S. KUTTY1,SANKAR CHATTERJEE2,PETER M. GALTON3 PAUL UPCHURCH4.BASAL SAUROPODOMORPHS (DINOSAURIA: SAURISCHIA) FROM THE LOWER JURASSIC OF INDIA: THEIR ANATOMY AND RELATIONSHIPS. Journal of Paleontology. 81: 1218-1240

Torsten H Struck. Data congruence, paedomorphosis and salamanders. 2007. Frontiers in Zoology 4:22

Richard J. Butler1,2,*,Peter M. Galton3,†,Laura B. Porro4,Luis M. Chiappe5,Donald M.Henderson6 andGregory M. Erickson7. Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America. Proc. R. Soc. B 277: 375-381

Ji Qiang, Philip J. Currie†, Mark A. Norell‡ & Ji Shu-An. 1998.Two feathered dinosaurs from northeastern China. NATURE 393: 753-761.

 Paul C. Sereno^*, Catherine A. Forster^*, Raymond R. Rogers^† & Alfredo M. Monetta^‡ 1993. Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria. Nature 361: 64 – 66

 P C Sereno, A B Arcucci. Dinosaurian precursors from the Middle Triassic of Argentina: Lagerpeton chanarensis. 1993. Journal of Vertebrate Paleontology  13: 385-399

 Robert R. Reisz,Diane Scott,1 Hans-Dieter Sues,David C. Evans, Michael A. Raath. 2005. Embryos of an Early Jurassic Prosauropod Dinosaur and Their Evolutionary Significance. Science. 309: 761-764.

 Robert M. Sullivan^a & Spencer G. Lucas^b. 1999. Eucoelophysis baldwini a new theropod dinosaur from the Upper Triassic of New Mexico, and the status of the original types of Coelophysis. Journal of Vertebrate Paleontology. 19:81-90.

Why Equids walk on their toenails…the curious case of the horse

Horses and other members of the genus Equus are unique in having a foot where functionally they are standing on their toenails of a single digit, the third toe. The hoofwall itself is analogous to a fingernail, the frog to the fingertip. Inside the hoofwall is the P3 bone, surrounded by a cartilaginous cushion, tendons and soft tissues. Other members of the order Perissodactyla (odd-toed), tapirs and rhinos and have several functional toes each with a hoof.

Tapir foot

http://www.tapirback.com/tapirgal/mixed/pix-nat/mxn0001.htm

http://extension.missouri.edu/p/G2740

Why then did equids come to this curious state, walking on the nails of one toe? Members of the artiodactyla (even-toed), the other order of hooved mammals, are a hodgepog of pigs, hippos, camels, giraffe, antelope, sheep, goats, cattle, pronghorn antelope which are not really antelope, and a strange group called chevrotains which superficially look remarkably like an early horse ancestor (no relation though!).

http://www.edinburghzoo.org.uk/animals/individuals/LesserMalayanChevrotain.html

Many members of this group, including antelopes are very fleet runners, much faster than a horse. A gazelle can run 60 mph just fine on its two twos. No other ungulates have gone as far as the Equidae in reduction of the foot. In other words, the multi-toed ancestors of horses and kin could have attained a respectable speed, enough to outrun a wolf or lion, without resorting to such extremes of footwear. Evolutionary reduction of the hoof should have reached its plateau at two toes. What pushed this development?

Modern horse (above)

Orohippus (above)

http://chem.tufts.edu/science/evolution/horseevolution.htm

Evolution of the hoof http://etc.usf.edu/clipart/57600/57608/57608_foot.htm

Some studies have suggested that digit reduction in equids is related more to increasing mass than locomotor adaption. Reduction to a single toe would allow a larger animal to maintain a cursorial locomotor style, as force channeled through a single outlet is more efficient and can better resist the greater stresses of a large galloping animal than force applied through several toes. Elements of the equid forelimb such as the interosseus tendon and sesamoid ligaments, as well as overall increased length of forelimb, shortening of the humerus, and a vertical scapula, combined with a streamlined foot, allowed equids to run efficiently for long distances, using less energy than would be expected for an animal its size.

Other elements of physiology support the idea of equids as long distance marathon runners. Several studies have indicated the prescence of a respiratory coupling or pump affect in trotting horses, a mechanism whereby the act of running helps to move air in and out of the lungs. Phases of respiration are coupled with the phases of locomotion allowing equids to breathe more efficiently than other animals when moving at speed.

 A Azzaroli. 1992. Ascent and decline of monodactyl equids: A case for prehistoric overkill.– Annales Zoologici Fennici 28:151-163.

J. J. Thomason. 1986. The Functional Morphology of the Manus in the Tridactyl Equids Merychippus and Mesohippus: Paleontological Inferences from Neontological Models. Journal Vertebrate Paleontology. 6: 143-161.

C.L. LAFORTUNA AND F. SAIBENE. 1991. MECHANICS OF BREATHING IN HORSES AT REST AND DURING EXERCISE. J. exp. Biol. 155: 245-259 

D.P. Attenburrow , V.A. Goss. 1994. The mechanical coupling of lung ventilation to locomotion in the horse.Medical Engineering & Physics. 16:188-192.

H. Milton. The Mechanics of horse legs. American Scientist. 75: 594-601

J.J. Thomason, J.E. Douglas and W. Sears. 2001. Morphology of the Laminar Junction in Relation to the Shape of the Hoof Capsule and Distal Phalanx in Adult Horses (Equus caballus). Cells Tissues Organs 168:295–311

M.T. Butcher, J.W. Hermanson, N.G. Ducharme, L.M. Mitchell, L.V. Soderholm and J.E.A. Bertram. 2009. Contractile behavior of the forelimb digital flexors during steady-state locomotion in horses(Equus caballus): An initial test of muscle architectural hypotheses about in vivo function. Comparative Biochemistry and Physiology. 152: 100-114

Shrew time

Shrews have the highest metabolism of all mammals, and must eat every hour or two. Maximum lifespan of most shrew species is around two years. Despite living on the fasttrack metabolically, shrews in common with all mammals run through roughly the same number of heartbeats in the course of an maximum lifespan, they just hit that limit much faster than an elephant! So logically a three-year old shrew at its death has reached the same age as the longest lived person (120), dog (20), elephant (60), horse (40), etc etc. So given the age of a shrew at 3 and human at 120, we should be able to calculate shrew time in terms of human time!

If, just for kicks we say that one human minute is one half-hour for a shrew, then a shrew day (24 hours) is 720 hours. There are 720 hours in 30 days. So one human day is equivalent to 30 shrew days or one months. If there are on average 365 days in a year, then a shrew year is equivalent to 1,0950 days or 30 years. A one year old shrew is roughly 30 years old! A three year-old shrew, the maximum lifespan, would be 90 in human years. Five hours for a shrew, the time in which it would starve without food, is equivalent to about 6 days.

 ———————————–

1 min = 1 hr

60min/hrX24 hours =1440 min per day

1 shrew day = 1440 hours

24 hours per day/1440 = 60 days

1 shrew day = 60 days/ 2 months

1 year = 365 daysX60 = 21,900 days

21,900/365 = 60 years

5 hrs = 60 minX5 = 300 min = 300 hours = 300/24 hrs = 12 days

——————————————

http://www.mnn.com/earth-matters/animals/photos/11-of-the-smallest-mammals-in-the-world/etruscan-shrew

———————————————-

Given that a mammals lifetime number of heartbeats are finite, we can also compare shrew time in people time and horse time by comparing heartrates. Taking the average from minimum and maximum shrew heartrates, the average hearrate is 964 bpm. Average human heartrate is 70 bmp. Shrew HR is about 15 times a human HR. So a shrew lives fifteen times faster than a human. One human minute would equal 15 shrew minutes. If there are 1440 minutes in a human day there would be 21600 minutes in a shrew day. 1 human day would be 15 shrew days. There would be 5475 shrew days in a human year. 5475 days comes out to 15 years. One human year equals 15 shrew years. A three-year old shrew would be 45 in human years.

In horse time…A horse has a HR around 40 bpm, about half a humans. A shrews HR is 25 times faster than a horses, so time moves 25 times faster. One horse minute equals 25 shrew minutes. One horse hour equals 1500 shrew minutes or 25 hours. One horse day equals 600 shrew hours or 25 days. One horse year equals 9125 hours or 25 shrew years.

A 1 year old shrew is 25 in horse time. A three-year old shrew is 75 in human time.

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835 + 1093/2 = 964 bpm

1 min = 15 min (1/4 hour)

1440 min in dayX15 min = 21600 min in shrew day

1 day = 15 shrew days

15X365 = 5475 shrew days

5475/365 = 15 years

15X2.75=41.25 years

1 year = 41.25 years

1 human minute (70) = 13 shrew minutues (984)

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40 bmp vs 984 = 25 times faster

1 min =25 min

1 hr = 1500 min/60min = 25 hours

25X24hrs = 600 hrs

1 day = 25 days

25X365 = 9125 days

1 year = 25 years

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1 bill 1,000,000,000 heartbeats

2 bill – 70 per minX1440 min in day = 100800 per dayX365=36,792,000 in year = 54 years

horse – 21024000 = 47 years

dog – 52560000 -20