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1. Oct 2017
2. www.scienceintheclassroom.org www.scienceintheclassroom.org
1. A) Position of the disk at pinch-off, ZP, versus Fr*, for four disk radii R(solid squares), and position of the disk when the column achieves maximum volume, ZMaxVol, versus Fr*, for R = 5 mm (open squares).

Fig 4 Tabs:

Figure A: Here, the position of the disk at pinch-off is higher for higher Fr(star). Fr(star) is the ratio of the time for the gravitational collapse to the time for upward motion of the disk. The longer the radius of the disk is, the higher the pinch-off height will be, hitting a maximum value at 1 where increasing the radius will not increase the height at pinch off. These values found in the experiment are compared to the "ideal" maximum value computed.

Figure B: The x-axis of this graph is time (in ms) of lapping, the y-axis is the volume of liquid column with respect to time. The different plots are showing the speeds from 6 to 102 cm/s. When the speed is highest the cat can drink more liquid. On average when the speed is between 10 to 58 cm/s the intake of volume is almost the same, around 0,20ml. When height of column is greater the take off volume is smaller.

Figure C: The x-axis of this graph is mass of animals and the y-axis is lapping frequency. As the mass of the animals increase the lapping frequency decreases as shown by the black line with a negative slope.

Next Questions: The researcher's found (and modelled) the mathematical and physical underpinning of this muscular hydrostatic system. This work can provide the basis for further design of robotics and models.

2. N. C. Heglund, C. R. Taylor, T. A. McMahon, Science 186, 1112 (1974)

This is a report that discusses stride frequency- number of foot contacts per second, of different animals. (365)

3. H. J. Chiel, P. Crago, J. M. Mansour, K. Hathi, Biol. Cybern. 67, 403 (1992).

This study is about developing quantitative model, a reptilian tongue to study muscular hydrostat (a functional movement, protrusion and retrusion, a form of lapping). (17)

4. D. Trivedi, C. D. Rahn, W. M. Kier, I. D. Walker, Appl. Bionics Biomech. 5, 99 (2008).

A detailed study, consider soft robots like octopus arms that have novel capabilities of performing numerous tasks using very basic phenomenon of osmosis. This work also implement use of soft robots as electroactive polymers. (642)

5. K. K. Smith, W. M. Kier, Am. Sci. 77, 28 (1989).

A detailed study about organs like tongues, trunks of elephants, etc. that do not have skeletal support but still manage to do elongation, shortening, bending types of activities. (624)

6. L. M. Day, B. C. Jayne, J. Exp. Biol. 210, 642 (2007).

The authors studied the position of the limb in the squeletton during locomotion in various felidae. Despites the very distinct size and weight, the position seems very similar and conclude that bigger species of felidae do not have more upright limbs than smaller one. (106)

7. M. Doube, A. Wiktorowicz-Conroy, P. Christiansen, J. R. Hutchinson, S. Shefelbine, PLoS ONE 4, e4742 (2009).

A study of the differential growth (allometry) of the limb bones in Felidae. They show that this allometry is link to the function of the bones and higly variant. (37)

8. J. Meachen-Samuels, B. Van Valkenburgh, J. Morphol. 270, 729 (2009).

The forms of the forelegs were used to determine anatomical differences in large prey, small prey or mixed prey. Researchers also investigated whether prey capture strategies affect the size of the forelegs. The results indicate that the large prey animal specialists have relatively strong forelegs compared to the smaller prey animal specialists, the small prey animal specialists have relatively long distal limbs for fast prey catching and the mixed prey animal specialists have intermediate values.

9. A. P. Russell, H. N. Bryant, G. L. Powell, R. Laroiya, J. Zool. (London) 236, 161 (1995).

This is a sutdy of the relation between the morphology of the skull and the maxillaire with the number of tooth and their place. They are more focus on the disparition of a premolar in the Lynx. (10)

10. P. Christiansen, J. S. Adolfssen, J. Zool. (London) 266, 133 (2005).

(Allometry : mathematical description of the growth of biological tissues.) The maximum bite forces were estimated from the skull sections of the animals and the flexural strength of the canines were calculated using models. Felids (cats, cheetah, lions) have canines that are stronger than canids (wolfs,dogs and so on) and ursids("bears") canines seem stronger than cats.

11. A. S. Ahl, Vet. Res. Commun. 10, 245 (1986).

Detailed study of the role of the vibrissae (the little tactils hairs) in a structural but mainly functionnal point of view. This study investigates many questions on various domestic animals. (118)

12. K. Ojima, F. Mitsuhashi, M. Nasu, Y. Suzuki, Ann. Anat. 182, 47 (2000).

Detailed study microscopical structure of the tongueon in the japanese cat. (8)

13. K. M. Hiiemae, A. W. Crompton, in Functional Vertebrate Morphology, M. Hildebrand, D. Bramble, K. Liem, D. B. Wake, Eds. (Belknap of Harvard Univ. Press, Cambridge, MA, 1985), pp. 262–290.

General review on the mechanism of chewing, food transport, and swallowing in mammals. It's related to the paper by the description of the transport intraorally, which is describe with precision. (318)

14. A. J. Thexton, A. W. Crompton, R. Z. German, J. Exp. Zool. 280, 327 (1998).

This is a review of the tongue mechanism of lapping in pigs. It focuses on the transition from suckling and drinking when mammals become adults (a process called weaning). There is a detailed analysis of the movement of the tongue and the implication of the muscles. (62)

15. J. G. M. Kooloos, G. A. Zweers, J. Morphol. 199, 327 (1989).

A detailed study on the drinking mechanismmallard. (26)

16. J. Heidweiller, G. A. Zweers, Condor 92, 1 (1990).

A study on the drinking mechanismzebra of fish and bengalese fish. (31)

17. T. L. Daniel, J. G. Kingsolver, E. Meyhöfer, Oecologia 79, 66 (1989)

A detail study on the drinking mechanism of buterflies (43).

18. J. G. Kingsolver, T. L. Daniel, Oecologia 60, 214 (1983).

A detailed study, on the drinking mechanism of hummingbirds. (110)

19. D. Cundall, J. Exp. Biol. 203, 2171 (2000)

A detailed study on the drinking mechanismon snakes. (15)

20. S. W. S. Gussekloo, R. G. Bout, J. Exp. Biol. 208, 3395 (2005).

The authors look for a link between the cranial morphology and the speed of feeding and drinking in palaeognathous birds. They conclude that the morphology is not link to a specific need for feeding and drinking. (48)

21. M. Prakash, D. Quéré, J. W. M. Bush, Science 320, 931 (2008).

The drinking mechanism of shorebirds. This last involves a beak motion that breaks the surface tension of a liquid and move the drop inside the mouth. They study how to optimise this process depending on the frequency of the tweezing and the beak geometry. (157)

22. J. A. W. M. Weijnen, Neurosci. Biobehav. Rev. 22, 751 (1998).

A detailed study on the drinking mechanism of rats, focusing on the frequency of licking depending on the environment. (72)

23. P. J. Bentley, T. Yorio, J. Exp. Biol. 79, 41 (1979)

The authors review how amphibians drink. They distinguish two ways of absorbing water and underline the predominance of skin absorption in amphibian hydration. Their observation show that amphibian seems to drink water to taste it's salinity. (number of citation are indicated in parentheses : (83))

24. A scaling argument predicts a maximum volume when the disk height reaches ZMaxVol/H ~ Fr* (16), in excellent agreement with observations

The authors find that the height of the column at its maximal volume is proportional to Fr. A higher Fr means the inertial force drawing the column upwards is higher, this increases the heigh at which the volume is maximum.

25. given the tongue’s lack of skeletal support (28). Complex movement in the absence of rigid components is a common feature of muscular hydrostats, which in addition to tongues include elephant trunks and octopus arms (28, 29).

Appendages without a rigid support structure, like bones, are characterized by a unique layout of muscle fibers that allow them to perform delicate tasks. Robotics experts are studying them to improve the dexterity of their robots. https://www.youtube.com/watch?v=SlSWFu0397E Example of an octopus` finesse and dexterity.

26. The Froude number is also relevant to swimming, for example, setting the maximum practical swimming speed in ducks (26), and to terrestrial legged locomotion.

To understand better this example, take a look again on what is "Froude number" on the Glossary section.

27. For example, the water-running ability of the Basilisk lizard depends on the gravity-driven collapse of the air cavity it creates upon slapping the water surface with its feet. The depth to which the lizard’s leg penetrates the surface depends on the Froude number, which in turn prescribes the minimum slapping frequency (25).

Water shifts in response to pressure. To run on water, lizards take wide, outward steps that help them maintain balance, to not trip.

28. the domestic cat’s inertia- and gravity-controlled lapping mechanism is conserved among felines

Inertia draws liquid upward into column (which reach the mouth). Faster lappings fails to maximize inertial entrainment. Slower lappings results in belated mouth closure that misses most of the fluid column.

29. We tested this –1/6 power-law dependence by measuring the lapping frequency for eight species of felines, from videos

The authors wanted to test the relation they found between the mass and the lapping frequency.

So in this experiments they calculated the lapping frequencies among different species of feline using videos available on the internet.

30. among the Felidae has been demonstrated for skull (20, 21) and limb bones (22).

Articles 20, 21 and 22 are used to justify the argument of that having isometry and (marginally positive) allometry among Felidae. Insteresting reading if you want to know more about the subject.

31. Gravity-driven drainage then reduces the rate of volume increase, and V is at a maximum when gravity and inertia balance (Fig. 4B).

During lapping, the volume of the water column depends on its height and its radius. After the initial phase in which the volume is proportional to the height of the column, gravity starts pulling water back water inducing the a reduction in column diameter. As such, the height of the column increases but its thickness decreases.

32. to defeat gravity and pull liquid into the mouth
33. When the disk is close to the bath (Z << H), the column is cylindrical and V increases as V/R3 = πZ/R (Fig. 4B inset).

In the first moments of a lap, while the water column height increases, the water has not yet started to collapse and its volume is proportional to its height. As such, the volume of the column increases linearly with Z, the height of the column.

34. we find that Fr* is indeed of order unity (0.4), using the experimentally measured values UMAX =78 cm s−1 and H = 3 cm (Fig. 2B) and a tongue size of R ≈ 5 mm (Fig. 1G).

Assuming that the cat closes its mouth at the highest point reached by the water column, the auhors related the lapping frequency of real cats to the parameters of their robotic disc dictacting the properties of the water column. They show that the lapping frequency of real cats is optimized to match the physical properties of the water column.

35. The sequence illustrates the formation (A to E) and pinch-off (F) of the liquid column. After pinch-off, part of the column collapses into the bath (G), which leaves a pendantlike drop attached to the disk (H).

Question : Which parameters influence the dimension of the water column and its pinch-off time ?

Description : Here we have a 'force game' between inertia and gravity : From A to E inertia is predominant and so the water can rise (column). At the point F, we have an equilibrium between gravity and inertia. By the point G, gravity is becoming predominant on inertia and the column is ready to collapse . Only a little quantity of water stays on the disk (which is representing the cat's tongue) here on the point H.

Variables : Here, H is the final height of the disk. The pinch-off time refers to the moment when the water column loses contact with the glass disk. Umax is the maximal speed the disk achieves during the ascent. Fr is the ratio between the time the column takes to collapse and the time it takes to ascend. Here, the value Fr = 0.6 informs us that the column fell more quickly than it rose.

Next question : What can we deduce from the results of this model ? Specifically, when should mouth closure happen in order to maximize water intake ?

36. For small disks (R = 2.5 and 5 mm), ZP/H increased linearly with Fr*, whereas large disks (R = 10 and 12.7 mm) reached the final height before pinch-off (ZP/H = 1). Theory also successfully predicts that pinch-off occurs close to the disk (Fig. 3).

With a small disk, the height of the water column at pinch off is proportional to the speed of the disk. For a larger disk the height of the water column is higher at a given speed than for a smaller disk. Because of the big width of a large disk it needs to go slower for the water column to reach the same height.

37. To test the proposition that the column dynamics are set by a competition between inertia and gravity, we compared the height of the disk (Z) at pinch-off, ZP, with that predicted from our scaling analysis.

To measure the impact of the inertia to gravity ratio, the authors compared the disk's height at pinch-off time observed in the experiments, with the one predicted with a simplified model.

38. The latter is possibly dictated by biological constraints, such as the need to keep whiskers dry to maintain their sensory performance (19) or to maximize peripheral vision while drinking.

The whiskers of a cat are incredibly sensitive; they act like a 'sixth sense' to detect sound vibrations or the tiniest gusts of wind. This can warn the cat of danger or help it track down prey. This method of lapping not only keeps the whiskers dry but also allows the head to face forward, so the cat can watch out for danger.

39. Experiments were therefore conducted over a range of Fr and H/R values (16), for a fixed lapping height, H = 3 cm, determined from observations (Fig. 2B).

The authors repeated the experiment, changing the values of Fr, which is the ratio of the forces of inertia (upward pull) to gravity (downward pull), and the aspect ratio (the height of the water column divided by the radius of the disk).

40. Estimation of the forces involved suggests that the fluid dynamics of lapping are governed by inertia and gravity, whereas viscous and capillary forces are negligible (16).

The authors calculated the Reynold's number and Bond's number. The Reynold's number compares the opposing effects of motion and viscosity. The high velocity and low viscosity of the water column means that viscosity is negligible in cat lapping. Similarly, the Bond's number compares the effect of surface tension and gravity on a fluid. The high Bond number here shows that surface tension has little impact on the shape of the column.

41. To help understand the mechanism of lapping, we performed physical experiments in which a glass disk of radius R (representing the tongue’s tip), initially placed on a water surface, was pulled vertically upward (Fig. 3).

This experiment simulated the movement of the tongue while lapping. The authors used a glass disk to model the overall shape of the tongue and a piston to simulate its movement . This way, they accturately simulated a real cat tongue. This strategy enables to change easily the model in order to understand the relative importance of each of them and find the optimum model.

42. The tongue accelerates as it leaves the water surface, attains a remarkable maximum speed of UMAX = 78 ± 2 cm s−1, then decelerates as it enters the mouth. Recordings of 10 adult individuals (16) yielded a lapping frequency f = 3.5 ± 0.4 s−1 and an ingested volume per lap V = 0.14 ± 0.04 ml.

The authors explains the characteristics of cat lapping that they observed by filming 10 cats. The lapping is characterised by the frequency, the maximal speed attained by the tongue during lapping, and the volume drunk by a cat for each lap.

43. domestic cat

An indoor feline that doesn't need to be distinguished from other felids.

44. We used high-speed imaging to capture the motion of both the tongue and liquid during lapping [Fig. 1 and movie S1 (16)].

The use of high-speed imaging (500 frames/second in this experiment) enables the researcher's to collect accurate images about the position of the cat's tongue and the volume of the water column for many different time steps.

45. Here, we report on the lapping mechanism of the domestic cat (Felis catus).

The authors used cameras to record the tongue's motion of the cat when lapping water. The images showed water adheres to the dorsal side of the tongue. The authors then tried to reproduce this mechanism of adhesion by lifting a disk placed on the surface of water.

46. Animals have developed a range of drinking strategies depending on

Variable means of water intake among terrestrial organisms can be checked here: http://www.viralnova.com/animals-drink-water/

47. and yields a prediction for the dependence of frequency on animal mass

In other words : the competition between inertia and gravity sets the lapping frequency and shows that there is a dependancy between frequency and animal mass. In general there is a balance.

48. inertia

Inertia is a Newtonian law of motion that describes the tendency of matter to be in an unchanging state of motion when not acted upon by external forces. This could either be an object moving along a trajectory or stationary.

49. J. Heidweiller, J. A. van Loon, G. A. Zweers, Zoomorphology 111, 141 (1992).

A detail study, on chicken, of the drinking mechanism in a morphological point of view. (18)

50. Fig. 2

Fig 2 Tabs:

Graphing technique : Here, kinematics refers to the figures that plot the position of the tongue's tip of the cat over time.

Question: How does the position of the tongue during the lapping and its velocity change through time ?

Results: Figure A shows the position of the tongue for multiple cycles of the lapping process over 3 seconds. Figure B shows one cycle of the lapping process and plots the speed of the tongue. The tongue first accelerates and then drops to the surface of the water with decreasing velocity. Then it accelerates as it comes back up, and finally slows down as it enters the mouth.

Next question: How could we create a physical model replicating this process in order to assess the importance of different parameters for water intake ?

51. Terrestrial animals have evolved diverse means to acquire water, including absorption through the skin (1) or extraction of moisture from food (2), but most rely on drinking (3–12).

Based on observational studies, the authors conclude that drinking is the most common mechanism of rehydration in terrestrial animals

52. conserved

Conservation in evolution refers to a trait of a species that remains unchanged over generations. It is maintained and passed down to the next generation because it is usually essential and helps the organism to survive.

53. We find (16) that ZP/H ~ Fr* for Fr* < 1 and ZP/H ~ 1 otherwise.

The authors were able to find a relationship between the height of the water column and its thickness and the size and speed of the robotic disk.

As such, their relationship can be used to predict the height of the water column based on chosen parameters of the robotic disc.

54. hydrophilic

Hydro refers to water. Phylic refers to member of the same group.

Hydrophylic is a substance that is attracted and mixes well with water.

55. H. D. Prange, K. Schmidt-Nielsen, J. Exp. Biol. 53, 763 (1970).

This study mainly focus on metabolic cost of the performance of an active animal system and the limitations on this performance. (156)

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3. Sep 2017
4. www.scienceintheclassroom.org www.scienceintheclassroom.org
1. interspecific scalings

Comparison of elative sizes of anatomical structures in different species.

2. the transition from trot to gallop obeys nearly the same scaling of frequency with mass as lapping, f = 4.5 M −0.14 (f in s−1, M in kg) (27).

In this video you can understand better the logic between the horse's transition: https://youtu.be/lO58ytuno6Y

3. Crucial in the drinking process is the role of the tongue, which in vertebrates is used in two distinctly different ways. Vertebrates with complete cheeks, such as pigs, sheep, and horses, use suction to draw liquid upward and use their tongue to transport it intraorally (13, 14). In contrast, vertebrates with incomplete cheeks, including most carnivores, are unable (after weaning) to seal their mouth cavity to generate suction and must rely on their tongue to move water into the mouth (13). When the tongue sweeps the bottom of a shallow puddle, the process is called licking (4). When the puddle is deeper than the tongue excursion into the liquid, it is called lapping (15).

Description on different ways how vertebrates drink water. Vertebrates with incomplete cheeks drink water differently from vertebrates with complete cheeks. The difference is the use of the tongue.

This is a video that illustrates vertebrates with incomplete cheeks drinking: https://www.youtube.com/watch?v=IzWsHxRlEqg

This is a video that illustrates vertebrates with complete cheeks drinking: https://youtu.be/3-88QG2ogYM?t=45s

4. also recognized in a 1940 Oscar-winning short film (17)

This is a short film called "Quicker 'n a Wink" and it shows cat lapping at 4:29. Also another good illustration for the physical process.

https://youtu.be/gspK_Bi0aoQ

5. The tip is free of filiform papillae (18)

Check out this picture to have a better glimpe: https://www.flickr.com/photos/nightmare/388846359

6. J. W. Glasheen, T. A. Mcmahon, J. Exp. Biol. 199, 2611 (1996).

The authors focus on the modulate ability of lizard to run on water depending on their weight. They conclude that the smaller one have a higher surpluses forces than the larger ones. (83)

7. Inertial entrainment

Inertial entrainment, (see inertia, already referenced) describes the physical dynamics of motion caught in stasis.

Entrainment uses the law of inertia as a method of synchronising two events. In this case, the water travelling in constant motion with the tongue.

8. Froude number

Froude number, a quantity without dimensions, describes water flowing in an open channel. It is calculated as a ratio of flow of inertia (the ease in which water flows) and gravity (water moving down a surface).

9. Fig. 1 The lapping process. (A to F) Snapshots showing the movement of the tongue of F. catus and the dynamics of the liquid column during a lapping cycle. Lapping occurs by fluid adhesion to the dorsal part of the tongue's tip and by lifting a liquid column through the tongue's upward motion, before jaw closure. Time elapsed from the first frame is given in the top left corner of each frame. (G) Photograph of the dorsal side of the tongue of F. catus, acquired under anesthesia (16). Only the smooth tip is used in lapping.

Figure 1 Tabs

Major Question: Though we can picture a cat or dog lapping water, how can the use of high speed imaging show how cats are really getting water into their mouth?

High-speed Photography: The use of high speed photography allowed the researchers take a very quick process and see it stationary, step-by-step.

Results: Photograph A: the tongue is leaving the mouth to approach the liquid. Photograph B: the back of the tip of the tongue hit the top of the liquid, but do not penetrate the surface. Photograph C: as the cat's tongue is pulled back into it's mouth, the water below it is pulled up also forming a thin column which the cat will later trap into it's mouth. Photographs D-E: the column of water being held up by the water attaching to the tongue and it's shape is even maintained after the tongue retreats back into the mouth. Photograph F: the column of liquid falling back down into the water after a portion is taken up by the cat's mouth. Photograph G: the smooth area of the tongue is the only portion used in lapping. The roughness of the rest of the tongue would not allow it to use this technique to drink.

Next question: Though these images give us a mechanical understanding of the process of a cat's water intake, how can we quantify these results?

10. A. J. Thexton, J. D. McGarrick, Arch. Oral Biol. 33, 331 (1988)

The movements of the tongue markers in relation to the palate were recorded. The transported liquids then collected between the soft palate and tongue before they were swallowed.

11. growth dynamics

Describes the growth and evolution of a particular phenomena.

12. The balance of inertia and gravity yields a prediction for the lapping frequency
13. marginally positive allomety

Allometry is the key word here. It studies not proportional body growth.

14. Gaussian profile

The Gaussian profile, commonly referred to as ‘the normal distribution’, is characterised by a graph representing a bell shaped curve. The ‘bell’ of the curve represents a probability distribution, giving the approximation of an event. In this case, the graph characterises the vertical velocity, where the highest point of the curve shows the likeliest vertical velocity of the cats tongue.

15. kinematics

A branch of physics that studies motion of objects.

16. Isometry

It's the study of proportional body growth.

17. The tongue’s vertical position during upward motion is well described by an error-function

An error function has an S-cure shape. The authors found that the motion of the tongue during its lifting (back in the mouth) resembles the S-shape of an error function.

18. This competition between inertia and gravity sets the lapping frequency

You tube video that precisely explains phenomenon of lapping. https://www.youtube.com/watch?v=vP-ozt0WJvQ

20. Drinking presents a challenge to land vertebrates

21. lapping

The intake of a liquid by an animal by way of the tongue.

22. environmental

Environmental refers to anything exterior to the skin of an organism. Environmental constraints are limits to the ability of an organism because of the environment they inhabit.

23. the semirigid hairlike structures that give a cat’s tongue its characteristic roughness

In first half of 2017, Blog by KQED science published a beautiful blog on why cat's tongue feel like sandpaper? You can check it here: https://ww2.kqed.org/science/2017/02/28/why-does-your-cats-tongue-feel-like-sandpaper/

24. Dimensional analysis reveals that two dimensionless parameters control lapping

In order to find parameters that characterise the lapping, the authors used the fact that dimension units (m, s , kg,...) are identical in both side of an equation (example, if A and B are in meter (m), A/B is dimensionless, A*B is in meter square (m^2)). So, in this case, the two parameters are dimensionless.

25. order unity

Order unity refers to the fact that these numbers are similar and close to the value of 1.

26. palate’s rugae

The palate's rugae refers to the roughness caused by wrinkles or skin folds on the upper palette of the cats mouth.

27. Consequently, the balance between inertia and gravity dictates the lapping frequency, f, by controlling the time of pinch-off

The authors were able to see from the column dynamics that a higher inertia (upward force) to gravity (downward force) ratio influences the pinch-off time, which is time at which the water column loses contact with the disk after its elevation.

28. nonreturn device

In mechanics, a nonreturn device refers to a valve that only allows flow in one direction.

29. line of best fit

A line of best fit is a line sumperimposed on a scatter plot that best represents the trend of the data.

30. caudally

Caudally refers to the back end of the organism.

31. physiological

Physiology refers to the area of biology studying the function of living organism and their constituent parts.

Physiological constraits are limits of the ability of the organism based on the function of the organism.

Adhesion refers to the attraction of the molecular properties of a liquid to a surface wall. This will define the particular adhesion between the liquid and the surface of the tongue.

Antonym: cohesion (water molecules attraction and hydrogen bond to other molecules of water).

33. temporal derivative

Derivative refers to the rate of the change of a function. Temporal refers to the time component of the function.

A temporal derivative is the rate of change of the function with respect to time.

34. Vertebrates

An animal in a large evolutionary group characterized by the possesion of a backbone/spinal column. Classes in this group include birds, reptiles, mammals, and fish.

35. dorsal

Dorsal refers to "back." Antonyms include: ventral, belly.